U.S. patent number 9,243,013 [Application Number 13/060,161] was granted by the patent office on 2016-01-26 for ionic compound, method for producing the same, and ion-conductive material comprising the same.
This patent grant is currently assigned to NIPPON SHOKUBAI CO., LTD.. The grantee listed for this patent is Yuji Hagiwara, Satoshi Ishida, Taisuke Kasahara, Hiromoto Katsuyama, Keiichiro Mizuta, Toshifumi Nishida, Takanori Ochi, Kazunobu Ohata, Taketo Toba. Invention is credited to Yuji Hagiwara, Satoshi Ishida, Taisuke Kasahara, Hiromoto Katsuyama, Keiichiro Mizuta, Toshifumi Nishida, Takanori Ochi, Kazunobu Ohata, Taketo Toba.
United States Patent |
9,243,013 |
Hagiwara , et al. |
January 26, 2016 |
Ionic compound, method for producing the same, and ion-conductive
material comprising the same
Abstract
The present invention provides a method of producing a
tetracyanoborate-containing ionic compound in a milder condition
more efficiently and less expensively than conventional methods,
and a tetracyanoborate-containing ionic compound having a reduced
content of impure components. An ionic compound of the present
invention is represented by the following general formula (I), has
a content of fluorine atom-containing impurities of 3 mol % or less
per 100 mol % of the ionic compound, and a method for producing an
ionic compound represented by the general formula (I) of the
present invention comprises a step of reacting starting materials
containing a cyanide and a boron compound. ##STR00001## (In the
formula, Kt.sup.m+ denotes an organic cation [Kt.sup.b].sup.m+ or
an inorganic cation [Ke].sup.m+; and m denotes an integer of 1 to
3.)
Inventors: |
Hagiwara; Yuji (Isumi,
JP), Ochi; Takanori (Isumi, JP), Ohata;
Kazunobu (Isumi, JP), Kasahara; Taisuke (Suita,
JP), Toba; Taketo (Takarazuka, JP), Mizuta;
Keiichiro (Akashi, JP), Katsuyama; Hiromoto
(Shimamoto-cho, JP), Ishida; Satoshi (Kyoto,
JP), Nishida; Toshifumi (Osaka, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hagiwara; Yuji
Ochi; Takanori
Ohata; Kazunobu
Kasahara; Taisuke
Toba; Taketo
Mizuta; Keiichiro
Katsuyama; Hiromoto
Ishida; Satoshi
Nishida; Toshifumi |
Isumi
Isumi
Isumi
Suita
Takarazuka
Akashi
Shimamoto-cho
Kyoto
Osaka |
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A |
JP
JP
JP
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
NIPPON SHOKUBAI CO., LTD.
(Osaka, JP)
|
Family
ID: |
41707265 |
Appl.
No.: |
13/060,161 |
Filed: |
August 21, 2009 |
PCT
Filed: |
August 21, 2009 |
PCT No.: |
PCT/JP2009/064678 |
371(c)(1),(2),(4) Date: |
February 22, 2011 |
PCT
Pub. No.: |
WO2010/021391 |
PCT
Pub. Date: |
February 25, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110150736 A1 |
Jun 23, 2011 |
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Foreign Application Priority Data
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Aug 22, 2008 [JP] |
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2008-214504 |
Sep 18, 2008 [JP] |
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2008-240014 |
Mar 9, 2009 [JP] |
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2009-055643 |
May 19, 2009 [JP] |
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2009-121465 |
Jun 5, 2009 [JP] |
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2009-136719 |
Jul 24, 2009 [JP] |
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2009-173577 |
Jul 30, 2009 [JP] |
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2009-178166 |
Jul 30, 2009 [JP] |
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2009-178167 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07F
9/65688 (20130101); H01B 1/122 (20130101); C07F
5/022 (20130101); C07F 5/02 (20130101); C07D
233/58 (20130101) |
Current International
Class: |
C07F
5/02 (20060101); H01B 1/12 (20060101); C07D
233/58 (20060101); C07F 9/02 (20060101); C07F
9/6568 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1358726 |
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Jul 2002 |
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CN |
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1751053 |
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Mar 2006 |
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CN |
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8-107048 |
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Apr 1996 |
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JP |
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2000-318080 |
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Nov 2000 |
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JP |
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2002-308884 |
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Oct 2002 |
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JP |
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2003-142100 |
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May 2003 |
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JP |
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2004-165131 |
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Jun 2004 |
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JP |
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2004-175666 |
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Jun 2004 |
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JP |
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2005-302950 |
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Oct 2005 |
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JP |
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2006-517546 |
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Jul 2006 |
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JP |
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2008-517002 |
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May 2008 |
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JP |
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Other References
Bernhardt et al., "Die Tetracyanoborate M[B(CN).sub.4],
M=[Bu.sub.4N].sup.+, Ag.sup.+, K.sup.+", Z. Anorg. Allg. Chem.,
2000, vol. 626, pp. 560-568. cited by applicant .
Bernhardt et al., "Die Reaktionen von M[BF.sub.4] (M=Li, K) und
(C.sub.2H.sub.5).sub.2O-BF.sub.3 mit (CH.sub.3).sub.3SiCN, Bildung
von M[BF.sub.x(CN).sub.4-x] (M=Li, K; x=1, 2) und
(CH.sub.3).sub.3SiNCBF.sub.x(CN).sub.3-x, (x=0, 1)", Z. Anorg.
Allg. Chem., 2003, vol. 629, pp. 677-685. cited by applicant .
Bernhardt et al., "Eine effiziente Synthese von Tetracyanoboraten
durch Sinterprozesse", Z. Anorg. Allg. Chem., 2003, vol. 629, pp.
1229-1234. cited by applicant .
Matar et al., "Ab initio studies of the electronic structure of the
quaternary system LiBC.sub.4N.sub.4", J. Alloys Compd., 2007, vol.
427, pp. 61-66. cited by applicant .
International Search Report issued Sep. 15, 2009 in corresponding
International Application No. PCT/JP2009/064678, of record. cited
by applicant .
Williams et al., "Synthesis of LiBC.sub.4N.sub.4, BC.sub.3N.sub.3,
and Related C-N Compounds of Boron: New Precursors to Light Element
Ceramics", J. Am. Chem. Soc., 2000, vol. 122, pp. 7735-7741. cited
by applicant .
Uznanski et al., "An Improved Preparation of Trimethylsilyl
Cyanide", Synthesis, 1978, pp. 154-155. cited by applicant .
Ue et al., "Anodic Stability of Several Anions Examined by Ab
Initio Molecular Orbital and Density Functional Theories", Journal
of the Electrochemical Society, 2002, vol. 149(12), pp.
A1572-A1577. cited by applicant .
Bessler Von E., "Darstellung und Eigenschaften von AgB(Cn).sub.4
und CuB(CN).sub.4" aka "Preparation and Properties of AgB(CN).sub.4
and CuB(CN).sub.4", Z. Anorg. Allg. Chem., 1977, vol. 430, pp.
38-42. cited by applicant .
Supplementary European Search Report issued Apr. 27, 2012 in
corresponding European Application No. 09808327.2. cited by
applicant .
Office Action issued Oct. 22, 2013 in corresponding Japanese
Application No. 2010-525722, with English translation thereof.
cited by applicant .
European Office Action issued Apr. 9, 2013 in corresponding
European Application No. 09 808 327.2. cited by applicant .
Chinese Office Action, with English translation, issued Feb. 28,
2013 in corresponding Chinese Patent Application No.
200980132280.9. cited by applicant .
Office Action issued May 14, 2013 in corresponding Japanese
Application No. 2008-240013, with English language translation
thereof. cited by applicant .
Chinese Office Action issued Dec. 25, 2013 in Application No.
200980132280.9 with its English translation. cited by applicant
.
Chinese Notice of Rejection issued Jun. 27, 2014 in corresponding
Chinese Application No. 200980132280.9 (with English translation).
cited by applicant .
Notice of Reasons for Rejection mailed Jan. 7, 2014 in
corresponding Japanese Application No. 2008-240013, with English
translation thereof. cited by applicant .
Decision of Rejection mailed Jan. 28, 2014 in corresponding
Japanese Application No. 2010-525722, with English translation
thereof. cited by applicant .
European Office Action issued Dec. 19, 2014 in corresponding
Application No. 09 808 327.2. cited by applicant .
Notice of Release of Pretrial Reexamination issued Aug. 12, 2014 in
corresponding Japanese Application No. 2010-525722 (with English
translation). cited by applicant .
Office Action issued Apr. 1, 2015 in corresponding Japanese
Application No. 2014-093193 (with English translation). cited by
applicant .
Notification of Reasons for Refusal issued Aug. 11, 2015 in
corresponding Japanese Patent Application No. 2010-525722, with
English translation. cited by applicant .
Decision to Dismiss the Amendment issued Aug. 18, 2015 in
corresponding Japanese Patent Application No. 2010- 525722, with
English translation. cited by applicant .
Japanese Notice of Reasons for Refusal issued Nov. 10, 2015 in
corresponding Japanese Patent Application No. 2010-575722 with
English Translation. cited by applicant.
|
Primary Examiner: Brooks; Clinton
Attorney, Agent or Firm: Wenderoth, Lind & Ponack,
L.L.P.
Claims
The invention claimed is:
1. A method for producing an ionic compound represented by formula
(I), comprising a step of reacting starting materials containing
trimethylsilyl cyanide, a boron compound, and an amine and/or
ammonium salt, wherein the boron compound is at least one selected
from the group consisting of M.sup.cBX.sup.c.sub.4, BX.sup.c.sub.3,
BX.sup.c.sub.3-complex, and B(OR.sup.13).sub.3, wherein M.sup.c
denotes a hydrogen atom or an alkali metal atom, X.sup.c denotes a
hydrogen atom, a hydroxyl group or a halogen atom, and R.sup.13
denotes a hydrogen atom or an alkyl group: ##STR00024## wherein
Kt.sup.m+ denotes an ammonium cation, and m denotes an integer of
1.
2. The method for producing an ionic compound according to claim 1,
wherein the starting materials contain ammonium salt.
3. The method for producing an ionic compound according to claim 2,
wherein the ammonium salt contains a halide ion as an anion.
4. The method for producing an ionic compound according to claim 1,
wherein the ammonium salt contains a halide ion as an anion.
5. The method for producing an ionic compound according to claim 1,
further comprising a step of bringing a crude product obtained by
reacting the starting materials into contact with an oxidizing
agent.
6. The method for producing an ionic compound according to claim 5,
wherein the oxidizing agent is hydrogen peroxide.
7. A method for producing an ionic compound containing an alkali
metal cation, comprising reacting starting materials containing
trimethylsilyl cyanide, a boron compound, and an amine and/or
ammonium salt to produce an ionic compound represented by formula
(I), wherein the boron compound is at least one selected from the
group consisting of M.sup.cBX.sup.c.sub.4, BX.sup.c.sub.3,
BX.sub.c.sub.3-complex, and B(OR.sup.13).sub.3, wherein M.sup.c
denotes a hydrogen atom or an alkali metal atom, X.sup.c denotes a
hydrogen atom, a hydroxyl group or a halogen atom, and R.sup.13
denotes a hydrogen atom or an alkyl group: ##STR00025## wherein
Kt.sup.m+ denotes an ammonium cation, and m denotes an integer of
1, and carrying out a cation exchange reaction, wherein the
ammonium cation contained in the ionic compound represented by
formula (I) is exchanged for the alkali metal cation.
Description
TECHNICAL FIELD
The invention relates to an ionic compound, more particularly, an
ionic compound having a tetracyanoborate anion and its production
method as well as an ion-conductive material using the same, an
electrolyte solution containing the same, and an electrochemical
device containing the material.
BACKGROUND ART
An ionic compound has been used for an ion conductor for various
kinds of battery cells based on ion conduction and has been
employed for electrochemical devices such as primary batteries and
batteries having charge/discharge mechanism, e.g., lithium (ion)
secondary batteries and fuel cells, and also electrolytic
capacitors, electric double layer capacitors, lithium ion
capacitors, solar cells, electrochromic display devices, etc. In
general, these electrochemical devices are each composed of a pair
of electrodes and an ion conductor formed between the
electrodes.
Examples of the ion conductor are electrolyte solutions and solid
electrolytes and those obtained by dissolving an electrolyte in an
organic solvent or a polymer compound or their mixture are used as
the ion conductor. In the ion conductor, the electrolyte is
dissolved and dissociated into a cation and an anion to exhibit ion
conductivity. A battery using such an ion conductor has been used
for portable electronic appliances such as lap-top type and palmtop
type computers, mobile phones, video cameras, etc., and along with
wide spread of these appliances, the necessity of lightweight and
powerful batteries has been increased. Further, in terms of
environmental issues, the importance of development of secondary
batteries with longer lives has been increased.
As an ionic compound to be used for the above-mentioned secondary
batteries or the like, lithium hexafluorophosphate (LiPF.sub.6) and
lithium tetrafluoroborate (LiBF.sub.4), which are electrolytic
salts, and cyanoborates containing alkali metals and organic
cations have been proposed. An ionic compound containing the
above-mentioned cyanoborate as an anionic component has a
characteristic as an ionic liquid, that is, the ionic compound is a
liquid even at room temperature and shows a characteristic of being
thermally, physically, and also electrochemically stable and thus
has been investigated for applications to various uses.
There have been proposed various methods to synthesize a compound
containing tetracyanoborate (TCB:[B(CN).sub.4].sup.-) among the
above-mentioned cyanoborates; that is, a method of reacting a
compound containing boron and an alkali metal cyanide (Z. Anorg.
Allg. Chem. 2000, vol. 626, p. 560-568), a method of carrying out
the above-mentioned reaction in the presence of a lithium halide
such as LiCl or the like (Japanese Patent Application Publication
(Translation of PCT Application) No. 2006-517546), a method of
reacting a boron compound such as KBF.sub.4, LiBF.sub.4, and
BF.sub.3. OEt.sub.2 with trimethylsilyl cyanide (Z. Anorg. Allg.
Chem. 2003, vol. 629, p 677-685, H. Willner, et al., (two others),
Z. Anorg, Allg. Chem. 2003, 629, p 1229-1234, J. Alloys Compd.
2007. 427. p 61-66, R. A. Andersen, et al. (four others), JACS.
2000. 122. p 7735-7741), etc.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
However, since an alkali metal cyanide has low reactivity with a
boron compound, it is needed to carry out the reaction under high
temperature condition around 300.degree. C. or to use an excess
amount of the alkali metal cyanide and thus there are problems that
it costs a high installation cost to introduce facilities with such
high durability as to deal with the above-mentioned reaction
condition and that impurities are easy to be produced. On the other
hand, there are also problems that trimethylsilyl cyanide is
expensive: the yield of the product is low: and that a salt of
tetracyanoborate and trimethylsilane is instable and easy to be
decomposed by heating.
In this connection, a method of synthesizing tetrabutylammonium
tetracyanoborate (Bu.sub.4NB(CN).sub.4) by using [NBu.sub.4]X,
BX.sub.3 (X.dbd.Br, Cl), and KCN is reported in Z. Anorg. Allg.
Chem. 2000, vol. 626, p. 560-568; however it is difficult to
synthesize the above-mentioned compound by a check experiment under
the condition described in the above-mentioned Document and
accordingly, a method of more stably obtaining a
tetracyanoborate-containing compound has been required.
Further, in the case an ionic compound is to be used for
electrochemical devices as described above, from a viewpoint of
reliably attaining good ion conductivity and preventing corrosion
or the like of peripheral members, it is required to lower impure
ionic components contained in the ionic compound. For example, in
the case the cyanoborate anion-containing compound described in the
above-mentioned Document is used as an electrolyte of an
electrolyte solution of the above-mentioned electrochemical
devices, it is particularly indispensable to lower cyanide ion
(CN.sup.-), halide ion, and metal ion.
However, in almost all of the conventionally employed methods,
fluorine-containing boron compounds are usually used as raw
materials. Particularly, in the case of synthesis of a compound
containing cyanoborate as an anion, a starting material sometimes
remains, or isolated CN.sup.- and water sometimes remain in the
compound and in such a case, heat resistance of the ionic compound
is lowered in some cases. Furthermore, these impurities remaining
in the electrolyte lower the ionic conduction capability and
corrode the peripheral members such as electrodes, resulting in a
cause of deterioration of the electrochemical capability.
In view of the above state of the art, it is an object of the
invention to provide a method of producing a
tetracyanoborate-containing ionic compound in a milder condition
more efficiently and less expensively than conventional methods and
a tetracyanoborate-containing ionic compound with a reduced content
of impure components.
Solution to the Problems
The ionic compound of the present invention which has solved the
above-mentioned problems is an ionic compound represented by the
following general formula (I), has content of fluorine
atom-containing impurities of 3 mol % or less per 100 mol % of the
ionic compound:
##STR00002## (wherein, Kt.sup.m+ denotes an organic cation
[Kt.sup.b].sup.m+ or an inorganic cation [Kt.sup.a].sup.m+; and m
denotes an integer of 1 to 3.)
Since the ionic compound of the invention has content of impurities
containing fuluorine atom (F atom) being lowered to an extremely
low level, deterioration of the ionic compound properties derived
from F atom and F atom-containing impurity, which are originated
from the starting materials, is hardly caused.
Further, it is preferable that the ionic compound has silicon
content of 2500 ppm or lower in the ionic compound. Furthermore,
CN.sup.- content is preferable to be 3000 ppm or lower; halide ion
content is preferable to be 500 ppm or lower; and additionally
water content is preferable to be 3000 ppm or lower.
An ion-conductive material containing the above-mentioned ionic
compound is one of the preferable embodiments of the present
invention.
A production method of the present invention is a method for
producing an ionic compound represented by the general formula (I),
which comprises a step of reacting starting materials containing a
cyanide and a boron compound.
The production method of the present invention includes a method
employing the starting materials containing trimethylsilyl cyanide
as the cyanide and further an amine and/or ammonium salt; a method
and; a method employing the starting materials containing, as the
cyanide, M.sup.a(CN).sub.n (M.sup.a denotes any of Zn.sup.2+,
Ga.sup.3+, Pd.sup.2+, Sn.sup.2+, Hg.sup.2+, Rh.sup.2+, Cu.sup.2+,
and Pb.sup.+; and n is an integer of 1 to 3); a method employing
the starting materials containing, as the cyanide, an ammonium
cyanide type compound represented as R.sub.4NCN (wherein R denotes
H or an organic group) and; a method employing the starting
materials containing hydrogen cyanide as the cyanide and further
containing an amine compound.
According to these production method, an ionic compound represented
by the above-mentioned general formula (I) is produced in a milder
condition, or more efficiently.
It is preferable that the production method of the present
invention further comprises a step of bringing a crude product,
which was obtained by reacting the starting materials, into contact
with an oxidizing agent. Furthermore, hydrogen peroxide is
preferable as the oxidizing agent.
Effects of the Invention
According to the production method of the present invention, an
ionic compound containing a tetracyanoborate ion
([B(CN).sub.4].sup.-) can be produced in a milder condition, or
more efficiently, or less expensively than conventional methods.
Consequently, it is made possible to industrially produce the ionic
compound of the invention.
Since the ionic compound of the invention has a wide potential
window and a content of impurities lowered to an extremely low
level, even in a case of using the ionic compound for various kinds
of uses such as electrolyte solutions and electrochemical devices,
stable characteristics (thermal, physical, electrochemical
characteristics, etc.) can be exerted without causing problems such
as corrosion of peripheral members.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1. A drawing showing LSV measurement result of Experiment
Example 6-1.
FIG. 2. A drawing showing LSV measurement result of Experiment
Example 6-2.
MODE FOR CARRYING OUT THE INVENTION
<Ionic Compound>
The ionic compound of the invention is an ionic compound defined by
the following general formula (I) and characterized in that the
content of fluorine atom-containing impurity is 3 mol % or less per
100 mol % of the ionic compound.
##STR00003## (wherein, [Kt].sup.m+ denotes an inorganic cation
[Kt.sup.a].sup.m+ or an organic cation [Kt.sup.b].sup.m+; and m
denotes an integer of 1 to 3).
Inventors of the present invention have made investigations on
characteristics of an ionic compound such as heat resistance and
electrochemical characteristics to find that the amount of
impurities derived from F atoms gets significantly engaged in
deterioration of the characteristics of the ionic compound and have
made further investigations on an ionic compound which hardly
causes such characteristic deterioration, consequently finding that
if the content of F atom-containing impurity is 3 mol % or lower
per 100 mol % of the ionic compound, the excellent characteristics
of the ionic compound containing tetracyanoborate ion as an anion
can be obtained sufficiently and the finding has now led to
completion of the invention.
In the invention, the F atom-containing impurity includes all of
those which contain F atoms such as free F atoms derived from the
starting materials for the above-mentioned ionic compound,
BF.sub.x(CN).sub.4-x (x denotes an integer of 1 to 3) which is
produced as a byproduct at the time of synthesizing the
above-mentioned ionic compound as well as compounds containing
BF.sub.3 and BF.sub.4 anions, etc. It is preferable that these
impurities are not contained in the ionic compound, an aimed
compound: and especially, it is more preferable that free F atoms
and a group of compounds having B--F bonds are not contained.
Particularly, it is furthermore preferable that the compounds
having B--F bonds are not contained in the ionic compound of the
invention. Since the compounds having B--F bonds are reacted with
water in the air and decomposed, if such compounds are contained in
the ionic compound of the invention, it may result in decrease of
the heat resistance and also it may cause a problem of corrosion of
the peripheral members by hydrogen fluoride generated at the time
of decomposition of the B--F bonds.
In the case that the ionic compound contains 3 mol % or more of the
impurity such as F atom and the above-mentioned F atom-containing
impurities, hydrogen fluoride gas may be generated to corrode the
peripheral members of various kinds of electrochemical devices or,
the characteristics (heat resistance and electric characteristics)
of the ionic compound itself may be deteriorated attributed to
these impurities. Accordingly, the content of the F atom-containing
impurity contained in the ionic compound of the invention is more
preferable as it is less, and it is preferable to be 1 mol % or
less per 100 mol % of the ionic compound and more preferable to be
0.1 mol % or less. It is most preferable that the F atom-containing
impurity is not contained (0 mol %) in the ionic compound of the
invention; however, if the amount of the F atom-containing impurity
is 0.0001 mol % or more, the effect on the characteristics of the
ionic compound is little and significant deterioration of the
characteristics is scarcely observed even if it is 0.001 mol % or
more.
The content of the impurities contained in the ionic compound of
the invention may be calculated by, for example, NMR spectrum.
Concretely, at first, .sup.11B--NMR spectrum of the ionic compound
of the invention is measured. Next, the value of integral of the
peak of B(CN).sub.4, which is an aimed compound, is defined as 100
mol % and compared with the value of integral of the peaks of
impurities having B--F bonds to calculate the content of the
impurities. Further, if .sup.19F-NMR spectrum is measured in the
same manner, the content of free F atoms and F-containing compounds
can be measured. In this connection, the calculation method of the
content of the impurities is not limited to the above-mentioned
methods and other methods may be employed. For example, it is also
possible to quantitatively measure the ion species containing F
atoms and free F atoms by ion chromatography. Therefore, the method
may include a method by determining the number of moles of the
B(CN).sub.4 compound from the total weight of the ionic compound,
calculating the weight of contained F anion by ion chromatography,
and calculating the content of the impurities by conversion of the
weight into the number of moles.
The ionic compound of the invention defined by the above-mentioned
general formula (I) is a compound defined by the above-mentioned
general formula (I) and obtained by reaction of trimethylsilyl
cyanide (TMSCN) and a boron compound, and the ionic compound of the
invention is preferable to be a highly pure ionic compound with
content of silicon (Si) of 2500 ppm or less in the ionic
compound.
Si contained in the ionic compound is derived from the starting
materials at the time of synthesizing the ionic compound (reference
to a production method of the invention described later). In the
case such impure components are contained, if the compound is used
for an electrolyte solution or the like, the ion conductivity may
be lowered in some cases. Therefore, it is desirable to lower and
remove the impure components as much as possible. Consequently, the
Si content in the ionic compound is more preferably 1000 ppm or
less and furthermore preferably 500 ppm or less.
Further, the high purity ionic compound of the invention is
preferable to have low content of cyanide ion (CN.sup.-) in
addition to the above-mentioned Si. The content of the cyanide ion
is preferably 3000 ppm or less. The cyanide ion may possibly lower
the ion conductivity by reaction with electrodes. The content of
the cyanide ion is more preferably 1000 ppm or less and even more
preferably 500 ppm or less.
Moreover, the high purity ionic compound of the invention is
preferable to have a low content of a halide ion in addition to the
above-mentioned Si and cyanide ion. Herein, "the content of a
halide ion" means the total of the concentrations of the respective
halide ions of F.sup.-, Cl.sup.-, Br.sup.-, and I.sup.-. As
described above, halide ions are reacted with electrode materials
and corrode the electrode materials and further, in the case
hydrogen ion exists in a system, halide ions may possibly lower the
pH of the electrolyte solution and dissolve the electrode materials
and deteriorate the capability of electrochemical devices in any
case.
Consequently, the halide ion amount in the ionic compound is more
preferable as it is less and the content of the halide ions in the
ionic compound is preferably 500 ppm or less, more preferably 100
ppm or less, and furthermore preferably 30 ppm or less. Among the
halide ions of F.sup.-, Cl.sup.-, Br.sup.-, and I.sup.-, the
content of F.sup.- and Cl.sup.- is preferably in the
above-mentioned range and the content of Cl.sup.- is particularly
preferably in the above-mentioned range.
In addition to the above-mentioned ionic components, the amount of
water (water concentration) contained in the ionic compound of the
invention is preferable to be 3000 ppm or less. Water remaining in
the ionic compound is electrolyzed, and generated hydrogen ions are
bonded with the above-mentioned halide ions to form hydrogen
halides. In addition, in an electrolyte solution, hydrogen ions and
halide ions exist while being dissociated, so that pH of the
electrolyte solution is lowered (acidic). As a result, due to the
produced acidic components in the electrolyte solution, the
electrode material is dissolved and the capability of an
electrochemical device is lowered. Consequently, the amount of
water contained in the ionic compound is better as it is lower and
it is preferably 1000 ppm or less and more preferably 500 ppm or
less.
The ionic compound of the invention defined by the above-mentioned
general formula (I) has low contents of impure ions attributed to
the starting materials and impurities which are inevitably mixed in
the synthesis process. Consequently, if the ionic compound of the
invention is used as an ion conductor of various kinds of
electrochemical devices, electrochemical devices with high
reliability and which hardly cause decrease of ion conductivity and
corrosion of peripheral members can be obtained.
Additionally, any of conventionally known measurement methods can
be employed for measuring the contents of the above-mentioned
impurities such as Si, halide ions and water; however examples of a
measurement method includes methods such as atomic absorption
spectrometry, ICP emission spectrometry (high-frequency
inductively-coupled plasma emission spectrometry) and ion
chromatography as described in Examples.
As represented by the above-mentioned general formula (I), the
ionic compound of the invention is a compound composed of an
organic or inorganic cation [Kt].sup.m+ and tetracyanoborate anion
[B(CN).sub.4].sup.-. The cation [Kt].sup.m+ may include organic
cations [Kt.sup.b].sup.m+ such as onium cation, and also inorganic
cations [Kt.sup.a].sup.m+ such as Li.sup.+, Na.sup.+, Mg.sup.2+,
K.sup.+, Ca.sup.2+, Zn.sup.2+, Ga.sup.3+, Pd.sup.2+, Sn.sup.2+,
Hg.sup.2+, Rh.sup.2+, Cu.sup.2+ and Pb.sup.+. Among them, those
containing onium cations or Li cation as [Kt].sup.m+ are easy to be
dissolved in an organic solvent and usable as a nonaqueous
electrolyte solution and therefore preferable.
The above-mentioned onium cations are preferably those defined by
the following general formula (II).
##STR00004##
In the formula, L denotes C, Si, N, P, S, or O; each R may be same
or different and denotes an organic group and respective R may be
bonded with each other; s denotes a number of groups denoted by R
bonded to L and satisfies s=(valence of L)+1-(number of double
bonds directly bonded to L) and an integer of 2 to 4. The valence
of L means 2 in the case L is S or O; 3 in the case L is N or P;
and 4 in the case L is C or Si.
The above-mentioned "organic group" denoted by R means a hydrogen
atom, fluorine atom or a group containing at least one carbon atom.
The above-mentioned "a group containing at least one carbon atom"
may be any group as long as the group contains at least one carbon
atom and may have other atoms such as a halogen atom and a
hetero-atom and also a substituent group. Examples of the
substituent group may include an amino group, imino group, amido
group, a group having an ether bond, a group having a thio-ether
bond, an ester group, hydroxyl group, an alkoxy group, carboxyl
group, carbamoyl group, cyano group, disulfide group, nitro group,
nitroso group, sulfonyl group, etc.
Examples of the onium cations defined by the above-mentioned
general formula (II) may be those defined by the following general
formulas:
##STR00005## (wherein, each R denotes a same or different organic
group and two or more of these may be bonded with each other) and
preferably onium cations containing N, P, S or O for L, more
preferably N for L. The onium cations may be used alone, or two or
more may be used in combination. Preferable examples among them are
onium cations defined by the following general formulas (III) to
(VI).
Examples may be at least one kind cation among 14 types of
heterocyclic onium cations defined by the following general
formulas (III):
##STR00006##
The organic groups denoted by R.sup.1 to R.sup.8 are same as those
exemplified in the general formula (II). More particularly, R.sup.1
to R.sup.8 denote a hydrogen atom, a fluorine atom, or an organic
group; and the organic group is preferably a straight or branched
or cyclic hydrocarbon group (excluding a group which forms a ring
by bonding groups denoted by R.sup.1 to R.sup.8) or a fluorocarbon
group having 1 to 18 carbon atoms; more preferably a hydrocarbon
group or a fluorocarbon group having 1 to 8 carbon atoms, and even
more preferably a hydrocarbon group or a fluorocarbon group having
1 to 9 carbon atoms. Further, the organic group may contain a
substituent group, a hetero atom such as nitrogen, oxygen or sulfur
atom, or a halogen atom as exemplified in the above-mentioned
general formula (II).
Examples may be at least one kind cation among 9 types of saturated
cyclic onium cations defined by the following general formulas
(IV):
##STR00007##
In the above-mentioned general formula, the organic groups denoted
by R.sup.1 to R.sup.12 are same or different and may be bonded with
one another.
Examples may be a aliphatic onium cation defined by the following
general formulas (V) in which the groups denoted by R.sup.1 to
R.sup.4 are same or different organic groups;
##STR00008##
Examples of the above-mentioned aliphatic onium cations (V) may be
quaternary ammoniums such as tetramethylammonium,
tetraethylammonium, tetrapropylammonium, tetrabutylammonium,
tetraheptylammonium, tetrahexylammonium, tetraoctylammonium,
triethylmethylammonium, methoxyethyldiethylmethylammonium,
trimethylphenylammonium, benzyltrimethylammonium,
benzyltributylammonium, benzyltriethylammonium,
dimethyldistearylammonium, diallyldimethylammonium,
2-methoxyethoxymethyltrimethylammonium, and
tetrakis(pentafluoroethyl)ammonium; tertiary ammoniums such as
trimethylammonium, triethylammonium, diethylmethylammonium,
dimethylethylammonium, and dibutylmethylammonium; secondary
ammoniums such as dimethylammonium, diethylammonium, and
dibutylammonium; primary ammoniums such as methylammonium,
ethylammonium, butylammonium, hexylammonium, and octylammonium; and
ammonium compounds such as N-methoxytrimethylammonium,
N-ethoxytrimethylammonium, N-propoxytrimethylammonium, and
NH.sub.4.
Among the onium cations of the above-mentioned (III) to (V),
nitrogen atom-containing onium cations are preferable; quaternary
ammoniums and imidazoliums are more preferable; and at least one
kind among 5 kinds of onium cations defined by the following
general formulas:
##STR00009## (wherein R.sup.1 to R.sup.12 are same as defined
above) is particularly preferable.
Particularly preferable examples among the above exemplified
ammoniums are alkyl quaternary ammoniums such as
tetraethylammonium, tetrabutylammonium, and triethylmethylammonium;
alkyl tertiary ammonium such as triethylammonium,
dibutylmethylammonium, and dimethylethylammonium; imidazoliums such
as 1-ethyl-3-methylimidazolium and 1,2,3-trimethylimidazolium; and
pyrrolidiniums such as N,N-dimethylpyrrolidinium and
N-ethyl-N-methylpyrrolidinium since they are easily made
available.
The ionic compound of the invention has excellent physical
properties such as heat resistance, electric conductivity, and
withstand voltage. In addition, these physical values differ more
or less depending on the type of the cation Kt.sup.m+ composing the
ionic compound; however the ionic compound of the invention
indicates withstand voltage of +2.0 V or higher by measurement of
potential window described later.
<Method for Producing Ionic Compound>
Next, a method for producing an ionic compound of the invention
will be described.
The method for producing an ionic compound of the invention is
characterized in that the ionic compound defined by the
above-mentioned general formula (I) is produced by reaction of
starting materials including a cyanide and a boron compound.
That is, the method for producing an ionic compound of the
invention includes a first production method for obtaining the
ionic compound defined by the above-mentioned general formula (I)
by reaction of a specified cyanide M.sup.a(CN).sub.n and a boron
compound; a second production method involving reaction of an
ammonium cyanide type compound and a boron compound; a third
production method involving reaction of trimethylsilyl cyanide
(TMSCN), an amine and/or ammonium salt, and a boron compound; and a
fourth production method involving reaction of hydrogen cyanide
(HCN), an amine, and a boron compound. According to these
production methods of the invention, an ionic compound containing
tetracyanoborate can be obtained in a milder condition, or more
efficiently, or less expensively than conventional methods.
Hereinafter, these production methods will be described
sequentially.
[First Production Method]
The method for producing an ionic compound of the invention is a
method for producing an ionic compound containing tetracyanoborate
ion and defined by the following general formula (I) and is
characterized in that the method involves reaction of starting
materials containing M.sup.a(CN).sub.n (M.sup.a denotes Zn.sup.2+,
Ga.sup.3+, Pd.sup.2+, Sn.sup.2+, Hg.sup.2+, Rh.sup.2+, Cu.sup.2+,
or Pb.sup.+; and n is an integer of 1 to 3), and a boron
compound.
##STR00010## (wherein, [Kt].sup.m+ denotes an organic cation
[Kt.sup.b].sup.m+ or an inorganic cation [Kt.sup.a].sup.m+; and m
denotes an integer of 1 to 3).
To obtain the ionic compound containing tetracyanoborate ion, the
inventors of the invention have found that use of a cyanide
compound M.sup.a(CN).sub.n containing specified metal ion (any one
of Zn.sup.2+, Ga.sup.3+, Pd.sup.2+, Sn.sup.2+, Hg.sup.2+,
Rh.sup.2+, Cu.sup.2+, and Pb.sup.+) in place of an alkali metal
cyanide such as potassium cyanide (KCN), which has been used
conventionally as a starting material, makes it possible to stably
obtain a compound defined by the above-mentioned general formula
(I) in mild reaction condition.
As the cyanide compound M.sup.a(CN).sub.n of the invention, a
cyanide compound of metal cation which is classified in metal
cation with low energy levels between HOMO-2nd HOMO, that is, soft
metal cations based on the HSAB rule, may be employed. It is
because use of a cyanide compound with the above specified metal
cation promotes the reaction quickly as compared with the case of
using an alkali metal cyanide compound. The reason for that the
above-mentioned metal cation is preferable is not made clear;
however the inventors of the invention suppose as follows.
In general, based on the HSAB rule, alkali metal ions are
classified in hard cations, and the specified metal contained in
the cyanide compound on the invention is classified in soft
cations. On the other hand, the tetracyanoborate anion (TCB), which
is a product, is classified in soft anions. It is therefore
supposed that since a combination of a soft acid and a soft base
tends to form a stable ionic compound, the reaction of the cyanide
compound in the invention tends to be promoted easily rather than
that using a conventionally employed alkali metal cyanide of a hard
cation such as Li.sup.+, Na.sup.+, and K.sup.+. Further, use of
cyanides of these metals of the invention as starting materials
makes it possible to obtain B(CN).sub.4 compound with few content
of impurities at a high yield.
<Cyanide>
Among the above-mentioned cyanide M.sup.a(CN).sub.n, preferable
examples include at least one selected from a group consisting of
Zn(CN).sub.2, Ga(CN).sub.3, Pd(CN).sub.2, Sn(CN).sub.2,
Hg(CN).sub.2, and Cu(CN).sub.2.
<Boron Compound>
The above-mentioned boron compound is not particularly limited as
long as it contains boron. Preferable to be used is at least one
selected from a group consisting of, for example,
M.sup.cBX.sup.c.sub.4 (M.sup.c denotes a hydrogen atom or an alkali
metal atom; X.sup.c denotes a hydrogen atom, a hydroxyl group, or a
halogen atom; hereinafter the same); BX.sup.c.sub.3,
BX.sup.c.sub.3-complex, B(OR.sup.13).sub.3 (R.sup.13 denotes a
hydrogen atom or an alkyl group; hereinafter the same),
B(OR.sup.13).sub.3-complex, Na.sub.2B.sub.4O.sub.7, ZnO
B.sub.2O.sub.3, and NaBO.sub.3.
Examples of M.sup.cBX.sup.c.sub.4 are HBF.sub.4, KBF.sub.4,
KBBr.sub.4, NaB(OH).sub.4, KB(OH).sub.4, LiB(OH).sub.4, LiBF.sub.4,
NaBH.sub.4, etc.; examples of BX % are BH.sub.3, B(OH).sub.3,
BF.sub.3, BCl.sub.3, BBr.sub.3, BI.sub.3, etc.; examples of
BX.sup.c.sub.3-complex are complexes of the above-mentioned
BX.sup.c.sub.3 with ethers such as diethyl ether, tripropyl ether,
tributyl ether, and tetrahydrofuran and amines such as ammonia,
methylamine, ethylamine, butylamine, hexylamine, octylamine,
dimethylamine, diethylamine, dibutylamine, dihexylamine,
dicyclohexylamine, trimethylamine, triethylamine, tributylamine,
triphenylamine, guanidine, aniline, morpholine, pyrrolidine and
methylpyrrolidine; examples of B(OR.sup.13).sub.3 are boric acid,
boron compounds having an alkoxy group of 1 to 10 carbon atoms,
etc. Preferable compounds among these compounds are NaBH.sub.4,
BH.sub.3, BF.sub.3, BCl.sub.3, BBr.sub.3, B(OMe).sub.3,
B(OEt).sub.3, Na.sub.2B.sub.4O.sub.7, and B(OH).sub.3 which have
relatively high reactivity; more preferable compounds are BF.sub.3,
BCl.sub.3, BBr.sub.3, etc., BX.sup.c.sub.3 in which X.sup.c is a
halogen atom, and B(OR.sup.13).sub.3 having an alkoxy group of 1 to
4 carbon atoms such as B(OMe).sub.3 and B(OEt).sub.3; and even more
preferable compounds are BCl.sub.3, B(OMe).sub.3, and B(OEt).sub.3.
The above-mentioned boron compounds may be used alone and two or
more of them may be used in combination. In terms of decrease of
the impurity amount derived from F, use of a compound containing no
F atom among these boron compounds is recommended.
In the first production method, at the time of reacting the
above-mentioned cyanide M.sup.a(CN).sub.n with a boron compound,
furthermore it is preferable to use an ionic substance defined by
the general formula: KtX.sup.b ([Kt].sup.m+ is a cation with m
valence; [X.sup.b].sup.m- is an anion with m valence; and m is an
integer of 1 to 3; and hereinafter, the same) as a starting
material.
Examples of the cation [Kt].sup.m+ composing the above-mentioned
ionic substance KtX.sup.b include organic cations [Kt.sup.b].sup.m+
such as onium cations and inorganic cations [Kt.sup.a].sup.m+ such
as Li.sup.+, Na.sup.+, Ca.sup.2+, K.sup.+, Zn.sup.2+, Ga.sup.3+,
Pd.sup.2+, Sn.sup.2+, Hg.sup.2+, Rh.sup.2+, Cu.sup.2+, and
Pb.sup.+. Among these, onium cations defined by the above-mentioned
general formulas (III) to (V) are particularly preferable as
[Kt.sup.b].sup.m+ composing the ionic substance in the invention.
When an ionic substance Kt.sup.bX.sup.b having an onium cation as
[Kt].sup.m+ is used for the starting material, it brings
advantageous consequence that an onium salt of [B(CN).sub.4].sup.-
which is an desired product can be obtained by one step reaction
and also cyanidation reaction is easily caused owing to mutual
action between M.sup.a(CN).sub.n and the ionic substance
Kt.sup.bX.sup.b.
The mixing ratio of the above-mentioned starting materials is
adjusted to be preferably 1:1 to 100:1 (cyanide
M.sup.a(CN).sub.n:boron compound, mol ratio). It is more preferably
1:1 to 50:1; furthermore preferably 1:1 to 20:1; and even more
preferably 1:1 to 10:1. If the mixing amount of the cyanide
M.sup.a(CN).sub.n is too low, the production amount of the aimed
ionic compound may possibly be low or byproducts (e.g.
tricyanoborate, dicyanoborate, etc.) may be produced. On the other
hand, if the mixing amount of the cyanide M.sup.a(CN).sub.n is too
high, the amount of impurities derived from CN is increased and it
tends to be difficult to refine the desired product.
In the case the ionic substance KtX.sup.b is contained in the
above-mentioned starting materials, the mixing ratio of the ionic
substance to the boron compound is preferably to be 100:1 to 1:100
(ionic substance: boron compound, mol ratio). It is more preferably
50:1 to 1:50 and furthermore preferably 20:1 to 1:20. In the case
the mixing amount of the ionic substance is too low, the production
amount of the aimed ionic compound may possibly be low and on the
other hand, if the mixing amount of the ionic substance is too
high, the amount of impurities derived from the ionic substance is
increased and it sometimes tends to be difficult to refine the
desired product.
To evenly promote the reaction in the method for producing an ionic
compound of the invention, it is preferable to use a reaction
solvent. The reaction solvent is not particularly limited as long
as it can dissolve the above-mentioned starting materials, and
water or an organic solvent may be used as the reaction solvent.
Examples of the organic solvent include hydrocarbon such as
toluene, xylene, benzene, and hexane; chloride such as chloroform
and dichloromethane; ether such as diethyl ether, cyclohexyl methyl
ether, dibutyl ether, dimethoxyethane, and dioxane; ester such as
ethyl acetate and butyl acetate; ketone such as 2-butanone and
methyl isobutyl ketone; alcohol such as methanol, ethanol,
2-propanol, and butanol; acetonitrile, tetrahydrofuran,
.gamma.-butyrolactone, dimethyl sulfoxide, dimethylformamide, etc.
The above-mentioned reaction solvents may be used alone or two or
more of them may be used in form of a mixture.
The condition at the time of reacting the starting materials is not
particularly limited and may be properly adjusted in accordance
with the advancing state of the reaction; however, for example, the
reaction temperature is adjusted to be preferably 0.degree. C. to
200.degree. C. It is more preferably 20.degree. C. to 150.degree.
C. and even more preferably 50.degree. C. to 130.degree. C. The
reaction time is adjusted to be preferably 0.2 hours to 200 hours,
more preferably 0.5 hours to 150 hours, and even more preferably 1
hour to 100 hours.
In the first production method, in the case the above-mentioned
metal cyanide and boron compound are used as the starting
materials, an ionic compound defined by the general formula:
Kt.sup.a[B(CN).sub.4].sub.m ([Kt.sup.a].sup.m+ is the metal cation
[M.sup.a].sup.n+ of the cyanide) is produced. Further, as described
above, in the case the starting materials include the ionic
substance KtX.sup.b ([Kt].sup.m+ is the onium cation
[Kt.sup.b].sup.m.sup.+ or the inorganic cation [Kt.sup.a].sup.m+)
or the produced ionic compound Kt.sup.a[B(CN).sub.4].sub.m
([Kt.sup.a].sup.m+ is the metal cation [M.sup.a].sup.n.sup.+ of the
cyanide) is cation-exchanged by reaction with the ionic substance
KtX.sup.b, an ionic compound Kt[B(CN).sub.4].sub.m having a desired
onium cation or inorganic cation can be obtained. The
above-mentioned cation exchange reaction with the ionic substance
will be described later.
Accordingly, the first production method of the invention includes
three embodiments: an embodiment of producing the ionic compound
Kt.sup.a[B(CN).sub.4].sub.m of the invention ([Kt.sup.a].sup.m+ the
metal cation [M.sup.a].sup.n+ of the cyanide) by reaction of the
above-mentioned cyanide M.sup.a(CN).sub.n and boron compound; an
embodiment of producing the ionic compound Kt[B(CN).sub.4].sub.m of
the invention ([Kt].sup.m+ is onium cation [Kt.sup.b].sup.m+ or the
inorganic cation [Kt.sup.b].sup.m+) by obtaining
Kt.sup.a[B(CN).sub.4].sub.m by reaction of the above-mentioned
metal cyanide M.sup.a(CN).sub.n and a boron compound and thereafter
cation-exchange reaction of the obtained compound with an ionic
substance KtX.sup.b: and an embodiment of producing the ionic
compound Kt[B(CN).sub.4].sub.m of the invention ([Kt].sup.m+ is
onium cation [Kt.sup.b].sup.m+ or the inorganic cation
[Kt.sup.a].sup.m+) by one-step reaction of the above-mentioned
metal cyanide M.sup.a(CN).sub.n, a boron compound, and an ionic
substance KtX.sup.b. Accordingly, the ionic compound
Kt.sup.m+[{B(CN).sub.4}.sup.-].sub.m of the invention obtained by
the first production method includes both cases, that is,
[Kt].sup.m+ is an onium cation [Kt.sup.b].sup.m+ and [Kt].sup.m+ is
an inorganic cation [Kt.sup.a].sup.m+.
According to the first production method of the invention using the
above-mentioned cyanide M.sup.a(CN).sub.n as a CN reagent, an ionic
compound having tetracyanoborate ion ([B(CN).sub.4].sup.-) can be
obtained even in a reaction condition in which it is impossible to
stably obtain an aimed compound by using an alkali metal cyanide
(KCN).
[Second Production Method]
Next, the second production method will be described. The second
method for producing an ionic compound of the invention is
characterized in that an ionic compound defined by the following
general formula (I) is obtained by reaction of an ammonium cyanide
type compound defined by the following general formula (VI) and a
boron compound.
##STR00011## (wherein, the bond between N--R is a saturated bond
and/or an unsaturated bond; t denotes the number of groups R bonded
to N, satisfies t=4-(number of double bonds bonded to N), and is an
integer of 3 to 4; respective R independently denote a hydrogen
atom or an organic group and two or more of them may be
bonded).
##STR00012## (wherein, [Kt].sup.m+ denotes an organic cation
[Kt.sup.b].sup.m+ or an inorganic cation [Kt.sup.a].sup.m+; and m
denotes an integer of 1 to 3).
In order to synthesize the ionic compound containing
tetracyanoborate ion, the inventors have found that use of an
ammonium cyanide type compound in place of an alkali metal cyanide
such as potassium cyanide which has been used conventionally as a
cyanide (CN) source makes it possible to obtain an ionic compound
defined by the above-mentioned general formula (I) efficiently at a
lower reaction temperature.
The inventors of the invention suppose the reason for that the
reaction is promoted in the milder condition than that in a
conventional method by using the ammonium cyanide type compound as
a cyanide source and the product is obtained more efficiently is as
follows. With respect to an alkali metal cyanide, the bond between
the alkali metal ion and cyano group (CN) is strong. On the other
hand, with respect to an ammonium type cyanide, since the N atom
bearing positive charge has steric hindrance, the cyanide ion is
hard to approach to the N atom and thus the bond between CN and N
atom is relatively weak. In this connection, in the reaction of
producing a tetracyanoborate, it is supposed that if free cyanide
ion in the reaction system is generated, the bond with the boron
compound tends to be formed easily and as a result, the desired TCB
is efficiently produced. Consequently, in the production method of
the invention using the ammonium type cyanide having a weak N--CN
bond, it is supposed that the cyanide ion can be released quickly
even in mild reaction condition and reaction is promoted to produce
TCB.
Consequently, the organic cation [Kt].sup.m+ composing the ionic
compound Kt[B(CN).sub.4].sub.m obtained by the second production
method of the invention includes those derived from the cations
contained in ammonium cyanide type compounds; those derived from
cations contained in boron compounds; and also those derived from
cations contained in ionic substances to be employed for cation
exchange reaction described later.
<Ammonium Cyanide Type Compound>
At first, an ammonium cyanide type compound defined by the
above-mentioned general formula (VI) will be described.
In the second production method, an ammonium cyanide type compound
[N--(R).sub.t]CN is used as a starting material. Use of the
ammonium cyanide type compound, as a CN source for TCB synthesis
reaction, makes it possible to obtain an ionic compound containing
tetracyanoborate [B(CN).sub.4].sup.- even in reaction condition in
which the desired compound cannot be obtained in the case an alkali
metal cyanide is used as a starting material.
In the ammonium [N.sup.+---(R).sub.t] composing the ammonium
cyanide type compound defined by the above-mentioned general
formula (VI), the N--R bond is a saturated bond and/or an
unsaturated bond; t denotes the number of groups R bonded to N,
satisfies t=4-(number of double bonds bonded to N), and is an
integer of 3 to 4; respective R independently denote a hydrogen
atom or an organic group and two or more of them may be bonded.
Additionally, the above-mentioned "organic group" may be same as
those exemplified in the above-mentioned general formula (II).
Further, R may be bonded with N, which is the center element of
ammonium, through a carbon atom composing the main structure of the
organic group R and also may be bonded with N through another atom
other than carbon or the above-mentioned substituent group.
Moreover, in the case two or more organic groups R are bonded, the
bonds may be a bond between a carbon atom composing the main
structure of the organic groups R and other atom, also a bond
between the carbon atom and a substituent group contained in the
organic group R, and further a bond between substituent groups
which are contained in two or more organic groups R
respectively.
Preferable examples of the ammonium [N.sup.+--(R).sub.t] having the
above-mentioned organic group R are those having the structure
defined by the following general formula (VII) to (IX).
(VII) That is, nine kinds of ammonium-type derivatives defined by
the following general formula in which t=3 and two R among three R
form a ring structure;
##STR00013## ##STR00014##
(VIII) Four kinds of ammonium-type derivatives defined by the
following general formula in which t=4 and two R among four R form
a ring structure;
##STR00015##
In the above-mentioned derivatives represented by the general
formulas (VII) to (VIII), R.sup.1 to R.sup.12 independently denote
a hydrogen atom or an organic group and two or more R may be
bonded; and
(IX) Alkylammonium derivatives defined by the following general
formula in which t=4 and four R are not bonded to one another;
##STR00016##
R.sup.1 to R.sup.4 composing the above-mentioned alkylammonium
derivatives independently denote a hydrogen atom or an organic
group.
Examples of the alkylammonium derivatives defined as (IV) include
ammoniums and ammonium compounds exemplified as the above-mentioned
aliphatic onium cations (V).
Preferable examples among the ammoniums defined as (VII) to (IX)
are those having the structure defined by the following six types
of general formulas.
##STR00017## (wherein, R.sup.1 to R.sup.12 denote as described
above).
In the above-mentioned general formulas, R.sup.1 to R.sup.12 denote
a hydrogen atom, a fluorine atom, or an organic group; and examples
of the organic group are same as those exemplified for the
above-mentioned general formula (III).
Particularly preferable examples among the above-exemplified
ammonium-containing ammonium cyanides, salts of alkyl quaternary
ammoniums and cyanide ion such as tetrabutylammonium cyanide,
tetraethylammonium cyanide, and triethylmethylammonium cyanide;
salts of alkyl tertiary ammonium and cyanide ion such as
triethylammonium cyanide, dibutylmethylammonium cyanide, and
dimethylethylammonium cyanide; salts of imidazolium and cyanide ion
such as 1-ethyl-3-ethylimidazolium cyanide and
1,2,3-trimethylimidazolium cyanide; and salts of pyrrolidinium and
cyanide ion such as N,N-dimethylpyrrolidinium cyanide and
N-ethyl-N-methylpyrrolidinium cyanide, since these salts are easily
made available.
The ammonium cyanide may be an ammonium cyanide containing a single
ammonium, or the ammonium cyanide containing two or more different
kinds of ammonium may be used in form of a mixture.
The ammonium cyanide can be synthesized by reaction of a compound
defined by the following general formula (X) and a metal cyanide
L.sup.p+[(CN).sup.-].sub.n(L.sup.p+ denotes a metal cation; p is 1
to 4 or preferably 1 or 2).
[Chemical Formula 16] [NR).sub.t].sub.IY (X) (wherein
[N--(R).sub.t] denotes same as defined by the general formula (VI);
Y denotes a halide ion, BF.sub.4.sup.-, PF.sub.6.sup.-,
SO.sub.4.sup.2-, HSO.sub.4, ClO.sub.4.sup.-, NO.sub.3.sup.-, or
R.sup.13O.sup.- (R.sup.13 denotes a hydrogen atom or an organic
group); l denotes 1 or 2; and additionally, R.sup.13 is same as
R.sup.1 to R.sup.12).
In the above-mentioned general formula (X), [N.sup.+--(R).sub.t]
corresponds with the ammonium cation of the above-mentioned
ammonium cyanide, and concrete examples of [N.sup.+--(R).sub.t]
include tetrabutylammonium, triethylmethylammonium,
tetraethylammonium, triethylammonium, dibutylammonium,
dimethylammonium, 1-ethyl-3-methylimidazolium,
N,N-dimethylpyrrolidinium, N,N-methylbutylpyrrolidinium, ammonium
(NH.sub.4.sup.+), morpholium, etc. Concretely, preferable examples
of the compounds (X) include tetrabutylammonium sulfoxide,
tetraethylammonium chloride, triethylammonium chloride,
1-ethyl-3-methylimidazolium bromide, etc.
In the above-mentioned metal cyanide L.sup.p+[(CN).sup.-].sub.n,
L.sup.p+ denotes an alkali metal ion, an alkaline earth metal ion,
Zn.sup.2+, Cu.sup.+, Cu.sup.2+, Pd.sup.2+, Au.sup.+, Ag.sup.2+,
Al.sup.3+, Ti.sup.4+, Fe.sup.3+, Ga.sup.3+, etc., and more
preferably an alkali metal ion, an alkaline earth metal ion,
Zn.sup.2+, Cu.sup.+, Cu.sup.2+, and Ag.sup.2+. Concrete examples of
the metal cyanide include KCN, LiCN, NaCN, Mg(CN).sub.2,
Ca(CN).sub.2, Zn(CN).sub.2, CuCN, Cu(CN).sub.2, etc.
The mixing ratio of the above-mentioned compound (X) and the metal
cyanide is adjusted to be preferably 40:1 to 1:40 (compound
(X):metal cyanide, mol ratio), more preferably 20:1 to 1:20, and
even more preferably 10:1 to 1:10.
The condition at the time of the above-mentioned reaction is not
particularly limited and for example, the reaction temperature is
adjusted to be preferably 0.degree. C. to 150.degree. C. and more
preferably 20.degree. C. to 100.degree. C. and reaction time is
adjusted to be preferably 0.01 hours to 20 hours and more
preferably 0.05 hours to 5 hours. Further, a reaction solvent may
be used or may not be used; preferable examples of the reaction
solvent are diethyl ether, dibutyl ether, tetrahydrofuran, dioxane,
dichloromethane, chloroform, carbon tetrachloride, ethyl acetate,
butyl acetate, acetone, 2-butanone, methyl isobutyl ketone,
acetonitrile, benzonitrile, dimethoxyethane, and water. These
reaction solvents may be used alone or two or more of them may be
used in combination. Additionally, use of two or more kinds of the
reaction solvents is one of preferable conditions of the
above-mentioned reaction.
<Boron Compound>
In the second production method of the invention, the ionic
compound defined by the above-mentioned general formula (I) is
synthesized by reaction of starting materials containing the
above-mentioned ammonium cyanide and boron compound. As the boron
compound, it is not particularly limited as long as the compound
contains boron and those same as exemplified in the first
production method can be employed.
The mixing ratio of the above-mentioned starting materials is
adjusted to be preferably 50:1 to 4:1 (ammonium cyanide: boron
compound, mol ratio). It is more preferably 20:1 to 4:1 and even
more preferably 10:1 to 4:1. If the mixing amount of the ammonium
cyanide is too low, the production amount of the desired ionic
compound may possibly be low or byproducts (e.g. tricyanoborate,
dicyanoborate, etc.) may be produced in some cases. On the other
hand, if the mixing amount of the ammonium cyanide is too high, the
amount of impurities derived from CN is increased and it tends to
be difficult to refine the desired product.
In the method for producing an ionic compound of the invention, to
evenly promote the reaction, it is preferable to use a reaction
solvent. The reaction solvent is not particularly limited as long
as it can dissolve the above-mentioned starting materials, and
water or an organic solvent may be used as the reaction solvent.
The organic solvent may be same as those exemplified in the first
production method. Particularly, preferable solvents are
hydrocarbon, ether, and ester. The above-mentioned reaction
solvents may be used alone or two or more of them may be used in
form of a mixture.
The condition at the time of reacting the starting materials is not
particularly limited and may be properly adjusted in accordance
with the advancing state of the reaction; for example, the reaction
temperature is adjusted to be preferably 30.degree. C. to
200.degree. C. It is more preferably 50.degree. C. to 170.degree.
C. and even more preferably 80.degree. C. to 150.degree. C. The
reaction time is adjusted to be preferably 0.2 hours to 200 hours,
more preferably 0.5 hours to 150 hours, and even more preferably 1
hour to 100 hours.
According to the second production method of the invention in which
the above-mentioned ammonium cyanide is used as a CN source, an
ionic compound having tetracyanoborate ion ([B(CN).sub.4].sup.-) is
obtained even in reaction condition of 200.degree. C. or lower at
which the desired product cannot be obtained if an alkali metal
cyanide is used.
[Third Production Method]
The third method for producing an ionic compound of the invention
is characterized in that an ionic compound defined by the following
general formula (I) is obtained by reaction of trimethylsilyl
cyanide (TMSCN), an amine and\or an ammonium salt, and a boron
compound.
##STR00018## (wherein, [Kt].sup.m+ denotes an organic cation
[Kt.sup.b].sup.m+ or an inorganic cation [Kt.sup.a].sup.m+; and m
denotes an integer of 1 to 3).
In synthesis of the ionic compound having tetracyanoborate ion, the
inventors of the invention have found that the ionic compound
defined by the above-mentioned general formula (I) can be obtained
at a high efficiency by using trimethylsilyl cyanide as a cyanide
(CN) source in place of an alkali metal cyanide such as potassium
cyanide, which is used conventionally, and carrying out reaction
with a boron compound in presence of an amine and/or ammonium
salt.
The inventors of the invention suppose the reason for that the
product is obtained by reaction of trimethylsilyl cyanide and a
boron compound under the presence of an amine and/or ammonium salt
at a higher yield than that by a conventional method is as
follows.
In the reaction for producing the tetracyanoborate, it is assumed
that a compound, which generates free cyanide ion in the reaction
system, is easy to form a bond with the boron compound and easy to
produce the desired TCB. Therefore, the inventors investigate the
bonding state between cyanide ion and alkali metal ion or
trimethylsilane. An alkali metal cyanide has no bulky substituent
group which hind the bond between the alkali metal ion and cyano
group (CN). Thus it is supposed that a strong bond is formed. On
the other hand, in trimethylsilyl cyanide, methyl groups are bonded
to cationic Si atom and the methyl groups create steric hindrance,
so that cyanide ion is hard to approach to the Si atom, and thus
the bond between CN and Si atom is supposed to be relatively weak.
Consequently, in the production method of the invention using
trimethylsilyl cyanide having a weak Si--CN bond, it is supposed
that the cyanide ion is released quickly and reacted to give
TCB.
The ionic compound composed of trimethylsilyl cation and TCB is
extremely instable and easy to be decomposed. However, in the
invention, it is supposed that since trimethylsilyl cation is
quickly replaced with ammonium cation, the TCB-containing ionic
compound is obtained stably. Further, although a detailed reason is
unclear, in the case of using an amine, it is supposed that the
amine catches protons generated from the starting materials and
intermediate products, and produces an ammonium compound by the
reaction. As a result, it is assumed that a stable TCB-containing
ionic compound is obtained in the same manner as that in the case
of using an ammonium salt. Because of these reasons, it is supposed
that the TCB production reaction is quickly promoted to produce the
ionic compound by carrying out the above-mentioned reaction in
presence of an amine and/or ammonium salt. In addition, in the
production method of the invention, since the reaction is carried
out in presence of an amine and/or ammonium salt, there is an
advantage that an ionic compound having ammonium as a cation is
obtained in one step.
<Trimethylsilyl Cyanide>
At first, trimethylsilyl cyanide as a starting material will be
described.
In the third production method, trimethylsilyl cyanide is used as a
starting material. Use of trimethylsilyl cyanide as a CN source for
TCB synthesis reaction makes it possible to obtain the ionic
compound having tetracyanoborate [B(CN).sub.4].sup.- even in a
reaction condition in which it is difficult to obtain a desired
compound in a case of using an alkali metal cyanide as a starting
material.
Trimethylsilyl cyanide to be used may be commercialized ones and
also those synthesized by conventional method. A method for
synthesizing TMSCN is not particularly limited; however, for
example, a method using starting materials containing a compound
having a trimethylsilyl group (TMS group) and hydrogen cyanide
(HCN) is preferable, since the method can synthesizes TMSCN more
economically.
Examples of the compound containing a TMS group may be TMSX.sup.1
(X.sup.1 is OR, a halogen atom, or hydroxyl group),
hexamethyldisilazane (TMS--NH-TMS), etc. Concretely, a method for
reacting TMSX.sup.1 (X.sup.1 is a halogen atom) with hydrogen
cyanide in presence of an amine such as triethylamine (reference to
the following reaction formula (XI-1); Stec, W. J., et al.,
Synthesis. 1978:154.) and a method for reacting
hexamethyldisilazane with hydrogen cyanide (reference to the
following reaction formula (XI-2)) can be employed.
TMSX.sup.1+HCN+Et.sub.3N.fwdarw.TMSCN+Et.sub.3NHX.sup.1 (XI-1)
TMS-NH-TMS+2HCN.fwdarw.2TMSCN+NH.sub.3 (XI-2)
Further, since the above-mentioned hexamethyldisilazane can work as
an amine, hexamethyldisilazane and a compound having trimethylsilyl
group may be used simultaneously (reference to the following
reaction formula (XI-3)). Consequently, ammonia produced as a
byproduct is trapped in the system and a problem of odor can be
suppressed and therefore, it is preferable.
TMSX.sup.1+[TMS-NH-TMS]+3HCN.fwdarw.3TMSCN+NH.sub.4X.sup.1
(XI-3)
The mixing ratio of the raw materials is adjusted to be preferably
20:1 to 1:20 (mol ratio), more preferably 10:1 to 1:10, and even
more preferably 5:1 to 1:5 of trimethylsilyl group and hydrogen
cyanide (HCN). That is, in the case hexamethyldisilazane is used,
or hexamethyldisilazane and a trimethylsilyl group-containing
compound are used in combination, the total amount of
trimethylsilyl groups contained in the raw materials and the
addition amount of hydrogen cyanide are controlled to be within the
above-mentioned range. The reaction temperature is preferably
-20.degree. C. to 100.degree. C. and more preferably 0.degree. C.
to 50.degree. C., and the reaction time is preferably 0.5 hours to
100 hours and more preferably 1 hour to 50 hours.
Additionally, in the third production method, a trimethylsilyl
group-containing compound is produced as a byproduct (e.g.
TMSX.sup.1, TMS-O-TMS, etc.; reference to the following
expression).
4TMSCN+BX.sup.2.sub.3+R.sub.4NX.sup.3.fwdarw.R.sub.4N[TCB]+3TMSX.sup.2+TM-
SX.sup.3 (XI-4) (X.sup.2 and X.sup.3 denote OR, a halogen atom, or
hydroxyl group).
Therefore, in the third production method, TMSCN regenerated by
reaction of the trimethylsilyl group-containing compound TMSX.sup.1
produced as a byproduct with HCN may be utilized as a starting
material. Because TMSCN is expensive and the production cost of the
ionic compound can be suppressed by recycling of TMSX.sup.1, which
is a byproduct.
<Boron Compound>
In the third production method of the invention, the ionic compound
defined by the above-mentioned general formula (I) is synthesized
by reacting starting materials containing the above-mentioned
TMSCN, amine and/or ammonium salt, and boron compound. The
above-mentioned boron compound is not particularly limited as long
as it is a boron-containing compound and those same as exemplified
in the first production method can be used.
The mixing ratio of the above-mentioned starting materials is
preferably 3:1 to 80:1 (TMSCN:boron compound, mol ratio). It is
more preferably 4:1 to 40:1 and even more preferably 4:1 to 20:1.
If the mixing amount of TMSCN is too low the production amount of
the desired ionic compound may possibly be low or byproducts (e.g.
tricyanoborate, dicyanoborate, etc.) may be produced in some cases.
On the other hand, if the mixing amount of TMSCN is too high, the
amount of impurities derived from CN is increased and it tends to
be difficult to refine the desired product.
<Amine and/or Ammonium Salt>
In the invention, the above-mentioned reaction of TMSCN and the
boron compound is carried out in presence of an amine and/or
ammonium salt. The amine becomes an ammonium salt in the reaction
system, and the produced ammonium salt is exchanged with
trimethylsilyl cation of a TCB compound comprising trimethylsilyl
as a cation, which is produced separately in the reaction system,
to obtain a stable ionic compound containing TCB at a high yield.
Further, since an amine and/or ammonium salt is used, an ionic
compound containing ammonium as a cation component can be obtained
in one step without carrying out cation exchange reaction.
Amines usable in the invention are preferably amines defined by the
following general formula (XII).
[Chemical Formula 18] NR).sub.u (XII)
In the general formula (XII), the bond between N--R is a saturated
bond and/or unsaturated bond; u denotes the number of groups R
bonded to N, satisfies u=3-(number of double bonds bonded to N),
and is 2 or 3; respective R independently denote a hydrogen atom, a
fluorine atom or an organic group and two or more R may be bonded
to form a ring. Additionally, examples of the above-mentioned
"organic group" may be same as those exemplified in the
above-mentioned general formula (II).
Examples of the amine defined by the above-mentioned general
formula (XII) include amine compounds (XIII) and (XIV) which have a
saturated or unsaturated cyclic structure in which two or more R
are bonded, and an amine compound (XV) in which R are
aliphatic.
(XIII) Amine compounds having a saturated or unsaturated cyclic
structure defined by the above-mentioned general formula (XII) in
which u is 3 and two or more R are bonded;
##STR00019##
In the general formulas (XIII-1) to (XIII-3), R.sup.1 to R.sup.3
denote a hydrogen atom, a fluorine atom, or an organic group; and
examples of the organic group are same as those exemplified for the
above-mentioned general formula (III).
Concrete examples of compound defined by the above-mentioned
general formulas (XIII-1) to (XIII-3) include compounds defined by
the general formula (XIII-1) such as pyrrole, pyrrolidine,
piperidine and morpholine; compounds defined by the general formula
(XIII-2) such as 1,4-diazabicyclo[2.2.2]octane (DABCO); compounds
defined by the general formula (XIII-3) such as
hexamethylenetetramine; and derivatives of these compounds.
(XIV) Amine compounds having an unsaturated cyclic structure
defined by the above-mentioned general formula (XII) in which u is
2 and two R are bonded.
##STR00020## (in the general formula (XIV), R.sup.1 and R.sup.2 are
same as those in the compound (XIII)).
Concrete examples of compound defined by the above-mentioned
general formula (XIV) include compounds having amidine structure
such as imidazole, imidazoline, pyrazole, triazole, pyrroline,
diazabicyclononene (DBN) and diazabicycloundecene (DBU), and their
derivatives; pyridine, pyridazine, pyrimidine, pyrazine, and their
derivatives.
(XV) Amine compounds defined by the following general formulas and
having a structure defined by the above-mentioned general formula
(XII) in which u is 2 or 3 and no R is bonded.
##STR00021## (in the above-mentioned general formulas (XV), R.sup.1
to R.sup.3 are same as those in the compound (VIII)).
Examples of the amine compounds defined by the above-mentioned
general formula (XV-1) in which u is 3 include trialkylamines such
as trimethylamine, triethylamine, tributylamine, tripropylamine,
diethylmethylamine, dibutylmethylamine, dihexylmethylamine, and
dipropylamine; dialkylamines such as dimethylamine, diethylamine,
dibutylamine, and dihexylamine; and monoalkylamines such as
methylamine, ethylamine, butylamine, pentylamine, hexylamine, and
octylamine. Examples of the compounds defined by the
above-mentioned general formula (XV-2) in which n is 2 include
guanidine and the like.
Preferable examples of amines defined by the above-mentioned
general formulas (VIII) to (XV) are aliphatic amines such as
triethylamine, tributylamine, butyldimethylamine, diethylamine,
dibutylamine, butylamine, hexylamine, octylamine, and guanidine;
cyclic amines such as piperidine, 1,4-diazabicyclo[2.2.2]octan
(DABCO), imidazoline, diazabicyclononene (DBN), and
diazabicycloundecene (DBU); and aromatic amines such as pyridine,
imidazole, methylimidazole, and pyrazine. Among them, aliphatic
amines such as triethylamine and dibutylamine have high basicity
and are economical and therefore preferable.
On the other hand, as an ammonium salt, ammonium salts having
ammonium cation defined by the above-mentioned general formulas
(VII) to (IX) can be employed and particularly, salts having
quaternary ammonium as a cation are preferable and concretely, one
or more compounds selected from a group consisting of compounds
defined by the following general formulas (XVII-1) to (XVII-5) are
preferable.
##STR00022##
In the formulas, respective R independently denote a hydrogen atom,
a fluorine atom, or an organic group; and examples of the organic
group defined by R in the above-mentioned general formulas are same
as those exemplified for the above-mentioned general formula
(II).
Concrete examples of an ammonium cation include ammonium,
triethylmethylammonium, tetramethylammonium, tetraethylammonium,
tetrabutylammonium, proton adduct of diazabicyclooctane,
imidazolium, methylimidazolium, ethylmethylimidazolium, pyridinium,
methylpyridinium, etc. and, especially preferable examples among
them are triethylmethylammonium, tetramethylammonium,
tetraethylammonium, tetrabutylammonium, proton adduct of
diazabicyclooctane, and ethylmethylimidazolium; and even more
preferable examples are triethylmethylammonium,
tetramethylammonium, tetraethylammonium, and
ethylmethylimidazolium.
Examples of an anion composing a salt with the above-mentioned
ammonium cations include a halide ion, cyanide ion (CN.sup.-),
hydroxy ion (OH.sup.-), cyanate ion (OCN.sup.-), thiocyanate ion
(SCN.sup.-), an alkoxy ion (RO.sup.-), sulfate ion, nitrate ion,
acetate ion, carbonate ion, perchlorate ion, an alkylsulfate ion,
an alkylcarbonate ion, etc. Especially, among these ions, a halide
ion is preferable and Cl.sup.- or Br.sup.- is particularly
preferable.
Examples of a preferable ammonium salt are those obtained by
combining the above-mentioned ammonium cations and the
above-mentioned anions and particularly preferable examples are
tetrabutylammonium bromide, triethylmethylammonium chloride,
tetraethylammonium chloride, ethylmethylimidazolium chloride,
ammonium methoxide, pyridinium hydroxide, and tetraethylammonium
cyanate.
The use amount of the above-mentioned amine and/or ammonium salt to
the boron compound is adjusted to be preferably 0.1:1 to 10:1
(boron compound: amine and/or ammonium salt, mol ratio). It is more
preferably 0.2:1 to 5:1 and even more preferably 0.5:1 to 2:1. If
the mixing amount of the amine and/or ammonium salt is too low,
removal of byproducts may become insufficient and the cation amount
may be too deficient to produce the desired product efficiently in
some cases. On the other hand, if the mixing amount of the amine
and/or ammonium salt is too high, the amine and/or ammonium salt
tends to remain as impurities.
To evenly promote the reaction in the method for producing an ionic
compound of the invention, it is preferable to use a reaction
solvent. The reaction solvent is not particularly limited as long
as it can dissolve the above-mentioned starting materials, and
water or an organic solvent may be used as the reaction solvent. As
the organic solvent, the solvents same as those used in the
above-mentioned first production method can be used. Not to mention
it, these reaction solvents may be used alone or two or more of
them may be used in form of a mixture.
The condition at the time of reaction of the starting materials is
not particularly limited and may be properly adjusted in accordance
with the advancing state of the reaction; however, for example, the
reaction temperature is adjusted to be preferably 0.degree. C. to
200.degree. C. It is more preferably 30.degree. C. to 170.degree.
C. and even more preferably 50.degree. C. to 150.degree. C. The
reaction time is adjusted to be preferably 0.2 hours to 200 hours,
more preferably 0.5 hours to 150 hours, and even more preferably 1
hour to 100 hours.
According to the third production method of the invention using the
above-mentioned TMSCN, amine and/or ammonium salt, and boron
compound as starting materials, an ionic compound having
tetracyanoborate ion ([B(CN).sub.4].sup.-) is obtained at a further
higher yield than that in the case of using an alkali metal cyanide
as the CN source, or that in the case of using TMSCN and an alkali
metal-containing boron compound as starting materials.
The ionic compound obtained by the third production method of the
invention has the structure defined by the above-mentioned general
formula (I), and comprises an organic cation or an inorganic cation
as the cation [Kt].sup.m+ and [B(CN).sub.4].sup.- as the anion. The
cation [Kt].sup.m+ may be derived from the boron compound (e.g. an
alkali metal ion), or from the ammonium salt (e.g. one of ammonium
cations defined by the above-mentioned general formulas (VII) to
(IX)), or an organic cation or an inorganic cation different from
them.
[Fourth Production Method]
Next, the fourth production method will be described. The fourth
method for producing an ionic compound of the invention is
characterized in that reaction of hydrogen cyanide, an amine, and a
boron compound is carried out to obtain an ionic compound defined
by the following general formula (I).
##STR00023## (wherein [Kt].sup.m+ denotes an organic cation
[Kt.sup.b].sup.m+ or an inorganic ion [Kt.sup.a].sup.m+; and m
denotes an integer of 1 to 3).
To synthesize the ionic compound containing tetracyanoborate ion,
the inventors have found that use of hydrogen cyanide in place of
an alkali metal cyanide such as potassium cyanide or trimethylsilyl
cyanide which has been used conventionally as a cyanide (CN) source
makes it possible to economically obtain an ionic compound defined
by the above-mentioned general formula (I).
Although not clearly understanding the reason why the ionic
compound containing tetracyanoborate can be obtained quickly by
using hydrogen cyanide, an amine and a boron compound, the
inventors of the invention suppose the reason as follows. In the
reaction system, at first hydrogen atom of hydrogen cyanide, which
is a starting material, is coordinated with lone pair electron of
nitrogen of the amine to form an ammonium complex. Next, the
ammonium complex and the boron compound are supposedly reacted to
produce the ionic compound containing TCB as a result. That is, in
the complex formed from hydrogen cyanide and an amine, the bond
between N--CN is relatively weak as compared with that of an alkali
metal cyanide, which has been used as a cyanide source.
Accordingly, it is supposed that if hydrogen cyanide and an amine
are used as starting materials, free cyanide ion can be formed
easily in the reaction system and as a result, the ionic compound
containing TCB is quickly produced.
The organic cation [Kt].sup.m+ comprising the ionic compound
Kt[B(CN).sub.4].sub.m obtained by the production method of the
invention includes those derived from the cations contained in
boron compounds; those derived from ammonium generated from
hydrogen cyanide and amines; and also those derived from cations
composing ionic substances to be employed for cation exchange
reaction described later.
<Hydrogen Cyanide>
As described above, in the fourth production method of the
invention, hydrogen cyanide is used as a cyanide source. Hydrogen
cyanide may be a gas or a liquid and may be used in form of a
solution obtained by dissolving hydrogen cyanide in water or an
organic solvent. In this connection, because of handling
convenience, liquid or solution type hydrogen cyanide is preferable
to be used.
<Amine>
Next, an amine will be described. In the fourth production method,
an amine is used as a starting material. An amine usable in the
invention is preferably amines defined by the above-mentioned
general formula (XII) and concrete examples of the amine include
amines same as those used in the third production method.
<Boron Compound>
In the fourth production method, starting materials containing the
above-mentioned hydrogen cyanide, amine, and boron compound are
reacted to synthesize an ionic compound defined by the
above-mentioned general formula (I). The above-mentioned boron
compound is not particularly limited as long as it is a compound
containing boron and those same as the boron compounds usable in
the above-mentioned first production method can be used.
In the fourth production method, the above-mentioned hydrogen
cyanide, amine, and boron compound are reacted to synthesize an
ionic compound defined by the above-mentioned general formula (I).
The mixing embodiment of the starting materials is not particularly
limited and an embodiment that hydrogen cyanide, an amine, and a
boron compound are loaded to a reaction container and an embodiment
that hydrogen cyanide and an amine are previously loaded to a
reaction container and thereafter, the boron compound is added to
the reaction system can be employed.
The mixing ratio of the amine to hydrogen cyanide is preferably
0.02:1 to 50: 1 (hydrogen cyanide:amine, mol ratio). It is more
preferably 0.05:1 to 20:1 and even more preferably 0.1:1 to 10:1.
If the mixing amount of hydrogen cyanide is too low the production
amount of the desired ionic compound may possibly be low or
byproducts (e.g. tricyanoborate, dicyanoborate, etc.) may be
produced in some cases. On the other hand, if the mixing amount of
hydrogen cyanide is too high, the amount of impurities derived from
CN is increased and it tends to be difficult to refine the desired
product.
The mixing ratio of the boron compound to hydrogen cyanide is
preferably 1:4 to 1:100 (boron compound: hydrogen cyanide, mol
ratio). It is more preferably 1:4 to 1:50 and even more preferably
1:4 to 1:20. If the mixing amount of boron compound is too low the
production amount of the aimed ionic compound may possibly be low
in some cases. On the other hand, if the mixing amount of boron
compound is too high, the amount of impurities derived from the
boron compound is increased and it tends to be difficult to refine
the desired product.
In the fourth method for producing an ionic compound of the
invention, to evenly promote the reaction, it is preferable to use
a reaction solvent. The reaction solvent is not particularly
limited as long as it can dissolve the above-mentioned starting
materials, and water or an organic solvent may be used as the
reaction solvent. The organic solvent may be same as those
exemplified in the first production method. Needless to say, the
above-mentioned reaction solvents may be used alone or two or more
of them may be used in form of a mixture.
The condition at the time of reaction of the starting materials is
not particularly limited and may be properly adjusted in accordance
with the advancing state of the reaction; however, for example, the
reaction temperature is adjusted to be preferably 30.degree. C. to
250.degree. C. It is more preferably 50.degree. C. to 170.degree.
C. and even more preferably 80.degree. C. to 150.degree. C. The
reaction time is adjusted to be preferably 0.2 hours to 200 hours,
more preferably 0.5 hours to 150 hours, and even more preferably 1
hour to 100 hours.
According to the fourth production method of the invention in which
hydrogen cyanide is used as a CN reagent, an ionic compound having
tetracyanoborate ion ([B(CN).sub.4].sup.-) can be obtained
economically as compared with conventional methods of using an
alkali metal cyanide and trimethylsilyl cyanide.
<Cation-Exchange Reaction>
The ionic compound obtained by the production method of the
invention may be subjected further to cation-exchange reaction. As
described below, since the characteristics of the ionic compound of
the invention depend on the cation type, an ionic compound with
different characteristics can be obtained easily by carrying out
cation exchange reaction.
As described in the first production method, if an ionic substance
KtX.sup.b ([Kt].sup.m+ denotes an organic cation or an inorganic
cation; [X.sup.b].sup.m- denotes an anion; and m denotes an integer
of 1 to 3) is used as a starting material, an ionic compound having
a desired cation can be obtained without additional performance of
cation-exchange reaction. These embodiments are also one of
recommended embodiments of the invention.
Accordingly, with respect to the ionic compound of the invention
defined by the above-mentioned general formula (I), in the case no
cation-exchange reaction is carried out, the cation [Kt].sup.m+ may
be cations derived from boron compounds and or cations derived from
cyanides M.sup.a(CN).sub.n (first production method); cations
derived from ammonium cyanide compounds, that is, cations of
various derivatives having structures defined by the
above-mentioned general formulas (VII) to (IX) (second production
method); cations derived from ammonium salts (third production
method); and ammonium cations produced from hydrogen cyanide and
amines (fourth production method).
On the other hand, in the case the above-mentioned each reaction is
carried out in presence of an ionic substance and, in the case the
cation-exchange reaction of the obtained ionic compound is carried
out after the above-mentioned reaction, the cation becomes the
cation [Kt].sup.m+ composing the ionic substance KtX.sup.b, that is
a conventionally known organic cation or an inorganic cation
[Kt].sup.m+ such as an alkali metal ion, and an alkaline earth
metal ion.
With respect to [Kt].sup.m+ comprising the ionic substance,
ammonium defined by the above-mentioned general formula
[N.sup.+--(R).sub.t] is preferable as an organic cation and alkali
metal ions such as Li.sup.+, Na.sup.+ and K.sup.+ and alkaline
earth metal ions such as Mg.sup.2+ and Ca.sup.2+ are preferable as
an inorganic metal cation. More preferable cations are onium
cations defined by the above-mentioned general formulas (III) to
(V) and ammonium type compound derivatives defined by the
above-mentioned general formulas (VII) to (IX).
On the other hand, preferable examples of the anion
[X.sup.b].sup.m- include a halide ion, cyanide ion (CN.sup.-),
hydroxy ion (OH.sup.-), cyanate ion (OCN.sup.-), thiocyanate ion
(SCN.sup.-), an alkoxy ion (RO.sup.-), sulfate ion, nitrate ion,
acetate ion, carbonate ion, perchlorate ion, an alkylsulfate ion,
an alkylcarbonate ion, etc. Among these ions, a halide ion is
preferable and Cl.sup.- or Br.sup.- is particularly preferable.
That is, those obtained by combining the above-mentioned
[Kt].sup.m+ and [X.sup.b].sup.m- are preferably employed as the
ionic substance KtX.sup.b and particularly preferable examples
include salts of alkyl quaternary ammonium and halide ion such as
tetrabutylammonium fluoride, tetrabutylammonium chloride,
tetrabutylammonium bromide, tetraethylammonium fluoride,
tetraethylammonium chloride, tetraethylammonium bromide,
triethylmethylammonium fluoride, triethylmethylammonium chloride,
and triethylmethylammonium bromide; salts of alkyl tertiary
ammonium and halide ion such as triethylammonium fluoride,
triethylammonium chloride, triethylammonium bromide,
dibutylmethylammonium fluoride, dibutylmethylammonium chloride,
dibutylmethylammonium bromide, dimethylethylammonium fluoride,
dimethylethylammonium chlorides and dimethylethylammonium bromide;
salts of imidazolium and halide ion such as
1-ethyl-3-methylimidazolium fluoride, 1-ethyl-3-methylimidazolium
chloride, 1-ethyl-3-ethylimidazolium bromide,
1,2,3-trimethylimidazolium fluoride, 1,2,3-trimethylimidazolium
chloride, and 1,2,3-trimethylimidazolium bromide; and salts of
pyrrolidinium and halide ion such as N,N-dimethylpyrrolidinium
fluoride, N,N-dimethylpyrrolidinium chloride,
N,N-dimethylpyrrolidinium bromide, N-ethyl-N-methylpyrrolidinium
fluoride, N-ethyl-N-methylpyrrolidinium chloride, and
N-ethyl-N-methylpyrrolidinium bromide. Further, as the ionic
substance, salts Kt.sup.aX.sup.b of halide ion and alkali metal ion
such as Li.sup.+, Na.sup.+ and K.sup.+ may be used. Additionally,
in terms of decrease of the amount of impurities derived from F, it
is recommended to use those containing no F atom among the
above-mentioned ionic substances.
The above-mentioned ionic substances KtX.sup.b may be used alone or
two or more of them may be used in combination.
The cation-exchange reaction may be carried out by reacting an
ionic compound obtained by the first to fourth production methods
of the invention with an ionic substance KtX.sup.b having a desired
cation.
In this case, the mixing ratio of the ionic compound
Kt[B(CN).sub.4].sub.m and the ionic substance KtX.sup.b at the time
of the cation-exchange reaction is adjusted to be preferably 50:1
to 1:50 (ionic compound Kt[B(CN).sub.4].sub.m:ionic substance
KtX.sup.b, mol ratio). It is more preferably 20:1 to 1:20 and even
more preferably 10:1 to 1:10. If the amount of the ionic substance
is too low, it may be sometimes difficult to quickly promote the
exchange reaction of the organic cation. On the other hand, if an
excess amount of the ionic substance is used, the unreacted ionic
substance contaminates the product and it tends to be difficult to
refine the product.
The exchange reaction of the organic cation may be carried out
merely by mixing the ionic compound Kt[B(CN).sub.4].sub.m and the
ionic substance KtX.sup.b in presence of a solvent and at that
time, the temperature may be 0.degree. C. to 200.degree. C. (more
preferably 10.degree. C. to 100.degree. C.) and reaction may be
carried out for 0.1 hours to 48 hours (more preferably 0.1 hours to
24 hours). Preferably used as the solvent may be organic solvents,
for example, ester type solvents such as ethyl acetate, isopropyl
acetate, and butyl acetate; ketone type solvents such as 2-butanone
and methyl isobutyl ketone; ether type solvents such as diethyl
ether, dibutyl ether, and cyclohexyl methyl ether; chlorine type
solvents such as dichloromethane and chloroform; aromatic type
solvents such as toluene, benzene, and xylene; and aliphatic
hydrocarbons such as hexane. These solvents may be used alone or
two or more of them may be used in combination. In this connection,
use of two or more reaction solvents is one of preferable
conditions for the above-mentioned reaction.
<Method for Producing Ionic Compound-treatment with Oxidizing
Agent>
The production method of the invention is preferably a method
further involving a step of bringing a product (ionic compound)
obtained by the above-mentioned first to fourth production methods
into contact with an oxidizing agent. In the case the
cation-exchange reaction is carried out successively to the first
to fourth production methods, the contact of the ionic compound,
which is the product, and an oxidizing agent may be carried out
before or after the cation-exchange reaction and may be carried out
both of before and after the cation-exchange reaction.
As described above, the impure ionic components contained in the
ionic compound deteriorate electrochemical devices and their
peripheral members for which the ionic compound is employed.
Consequently, it may possibly result in decrease of the performance
of the electrochemical devices. Further, in the production method
of the invention, a cyanide M.sup.a(CN).sub.n (first production
method), an ammonia cyanide (second production method), TMSCN
(third production method), and hydrogen cyanide (fourth production
method) are used as starting materials. Consequently, free cyanide
ion (CN.sup.-) or the like derived from starting materials may
sometimes remain in the product or impurities inevitably mixed in
the production process may possible exist in some cases. The ionic
compound of the invention is sometimes used as a constituent
material for electrochemical devices and the impurities such as
CN.sup.- existing in the ionic compound decreases the ion
conductivity and corrodes electrodes to deteriorate the
electrochemical capabilities.
Therefore, the inventors of the invention have made investigations
to lower the content of these impurities of ionic components in the
ionic compound. In general, an organic compound tends to be
oxidized and decomposed in the presence of an oxidizing agent and
it is supposed that an ionic compound containing tetracyanoborate
[B(CN).sub.4].sup.- as an anion is also similarly oxidized and
decomposed. Accordingly, the impurities of ionic components in the
ionic compound are removed in form of an alkali metal salt (NaCN,
NaCl) by transferring it to a water layer by extraction treatment
using an aqueous NaOH solution or the like; however cyanide ion
(CN.sup.-) is weakly acidic and the solubility of its salt with an
alkali metal in water is not so high and therefore, the extraction
efficiently is low. Further, to sufficiently lower the impurity
amount, it is needed to repeat the extraction process a plurality
of times and it results in a problem that the yield of the ionic
compound is lowered.
Nevertheless, the inventors of the invention have found that the
ionic compound containing TCB as an anion unexpectedly has higher
stability than common organic compounds to an oxidizing agent, and
therefore, excess cyanide ion (CN.sup.-) contained in the product
can be decomposed by bringing the ionic compound into contact with
an oxidizing agent after the synthesis. Moreover, the content of
impurities inevitably mixed in the starting materials and in the
synthesis process can be lowered.
Especially, in the case the product obtained by reaction of
trimethylsilyl cyanide and a boron compound and an oxidizing agent
are brought into contact with each other, a highly pure ionic
compound with lowered impurities such as silicon and halide ions
and water is obtained.
<Treatment with Oxidizing Agent>
Examples of an oxidizing agent to be used for the above-mentioned
treatment with an oxidizing agent may be peroxides such as hydrogen
peroxide, sodium perchlorate, peracetic acid, and
meta-chloroperbenzoic acid (mCPBA); manganese compounds such as
potassium permanganate and manganese oxide; chromium compound such
as potassium dichromate; halogen-containing compounds such as
potassium chlorate, sodium bromate, potassium bromate, sodium
hypochlorite, and chlorine dioxide; inorganic nitrogen compounds
such as nitric acid and chloramine; acetic acid, and osmium
tetraoxide. Among these compounds, peroxides are preferable and
hydrogen peroxide and sodium perchlorate are more preferable.
Especially, in the case of using hydrogen peroxide as the oxidizing
agent, impurities such as chloride ion (Cl.sup.-) and cyanate ion
(NCO.sup.-) are efficiently distributed in the hydrogen
peroxide-aqueous layer and the extraction efficiency of the ionic
compound is improved and therefore it is particularly preferable.
Furthermore, in the case of using hydrogen peroxide, those
absorbing moisture and components easy to be hydrated among
impurities are efficiently distributed in the hydrogen
peroxide-aqueous layer and therefore, the purity of the ionic
compound is increased and at the same time, the water content is
also easily decreased in the ionic compound.
The oxidizing agent may be in solid state or liquid state, and in
the case of solid state, it may be dissolved in a solvent. An
oxidizing agent solution obtained by dissolving a liquid-state
oxidizing agent or a solid-state oxidizing agent in a solvent may
be used after being further diluted.
Although it depends on the impurity amount (especially, CN.sup.- or
the like) in the crude ionic compound, the use amount of the
oxidizing agent is preferably 1 part by weight to 1000 parts by
weight, more preferably 10 parts by weight to 500 parts by weight,
further more preferably 20 parts by weight to 300 parts by weight,
and even more preferably 50 parts by weight to 100 parts by weight
per 100 parts by weight of the crude ionic compound. Additionally,
in the case that the oxidizing agent amount is too high, the ionic
compound may possibly be decomposed. On the other hand, if the
oxidizing agent amount is too low, it is difficult to sufficiently
lower the excess ionic components and impurities in some cases. In
this connection, "crude ionic compound" means the component
obtained by removing a solvent from a reaction solution after the
synthesis. The treatment with an oxidizing agent may be carried out
without removal of the reaction solvent or the like after the
synthesis or after other refining treatment described below.
The treatment with an oxidizing agent is not particularly limited
as long as the crude ionic compound and an oxidizing agent are
brought into contact with each other, and the crude ionic compound
after synthesis as it is may be brought into contact with an
oxidizing agent, or a solution of the crude ionic compound is
prepared and the obtained crude ionic compound solution may be
mixed with an oxidizing agent for the contact. That is, a contact
embodiment may include an embodiment that a solid-state oxidizing
agent is added to the crude ionic compound solution to bring both
into contact with each other; an embodiment that the crude ionic
compound solution and an oxidizing agent solution are mixed to
bring both into contact with each other; and an embodiment that the
crude ionic compound in solid state is added to a oxidizing agent
solution to bring both into contact with each other. Additionally,
a solvent for dissolving the crude ionic compound is preferably a
solvent to be used for treatment with activated carbon described
below.
As described above, the ionic compound of the invention has high
tolerability to an oxidizing agent as compared with common organic
substances; however excess contact with an oxidizing agent becomes
a cause of decomposition of the ionic compound. Consequently, in
terms of suppression of decomposition of the ionic compound, it is
recommended to carry out the treatment with an oxidizing agent at
low temperature within a short time. For example, the treatment
with an oxidizing agent is carried out preferably at a temperature
equal to or lower than the reaction temperature at the time of
synthesizing the ionic compound, and more preferably at a
temperature equal to or lower than the boiling temperature of the
solvent. Concretely, it is preferably 0.degree. C. to 150.degree.
C., more preferably 0.degree. C. to 130.degree. C., furthermore
preferably 10.degree. C. to 100.degree. C., and even more
preferably 10.degree. C. to 80.degree. C.
<Other Refining Methods>
In the production method of the invention, to further decrease the
impurity amount in the ionic compound, conventionally known
refining methods other than the above-mentioned treatment with an
oxidizing agent may be employed. Examples of conventionally known
refining methods may include washing with water, an organic
solvent, and their mixed solvent; an adsorption purification
method; a re-precipitation method; a separatory extraction method;
a re-crystallization method; a crystallization method; and
chromatography. These refining methods may be carried in
combination.
In the case the above-mentioned another refining method is employed
in combination, the timing conducting the another refining method
is not particularly limited and any of the following embodiments
may be employed: before contact of the crude ionic compound and an
oxidizing agent; after contact of the crude ionic compound and an
oxidizing agent; and both before and after contact of the crude
ionic compound and an oxidizing agent.
For example, in the case an adsorption purification method is
employed, examples of an adsorbent may include activated carbon,
silica gel, alumina, zeolites, and the like. Among them, adsorption
treatment using activated carbon as an adsorbent (treatment with
activated carbon) is preferable since contamination of the ionic
compound with impurities is little.
The activated carbon usable for the adsorption treatment is not
particularly limited. The shape of the activated carbon is not
particularly limited as long as it has a wide surface area and may
include powder-like, milled, granulated, pelletized, and spherical
shapes and among these shapes, a powder-like activated carbon is
preferable to be used because of a wide surface area. Further, the
activated carbon is preferably those having a surface area of 100
m.sup.2/g or higher, more preferably those having a surface area of
400 m.sup.2/g or higher, and even more preferably those having a
surface area of 800 m.sup.2/g or higher. To avoid contamination of
the ionic compound with impurities contained in the activated
carbon, it is preferable to employ activated carbon with little
impurity content and one example of such an activated carbon is
Carborafin (registered trade name)-6 manufactured by Japan
EnviroChemicals, Ltd.
The use amount of the activated carbon is preferably not less than
1 part by weight and not more than 500 parts by weight; more
preferably not less than 10 parts by weight and not more than 300
parts by weight; and even more preferably not less than 20 parts by
weight and not more than 200 parts by weight per 100 parts by
weight of the crude ionic compound.
The treatment with activated carbon is preferably carried out for
the crude ionic compound immediately after synthesis and before the
treatment with an oxidizing agent. From a viewpoint that the effect
of the treatment with activated carbon is caused efficiently, it is
recommended that the crude ionic compound is subjected to the
treatment with activated carbon while being dissolved or dispersed
in a solvent.
A solvent usable for the treatment with activated carbon is not
particularly limited; however a solvent in which the crude ionic
compound can be dissolved is preferable. Examples include water;
aliphatic mono-alcohols such as methanol, ethanol, n-propyl
alcohol, isopropyl alcohol, 1-butanol, sec-butanol, tert-butanol,
1-pentanol, 2-pentanol, 3-pentanol, 3-methyl-1-butanol,
3-methyl-2-butanol, 2-methyl-1-butanol, tert-amyl alcohol,
neopentyl alcohol, 1-hexanol, 2-hexanol, 3-hexanol,
2-methyl-1-pentanol, 3-methyl-3-pentanol, 4-methyl-2-pentanol,
3,3-dimethyl-2-butanol, 1-heptanol, 2-heptanol, 3-heptanol,
2-methyl-3-hexanol, 2,4-dimethyl-3-pentanol, 1-octanol, 2-octanol,
3-octanol, 2-ethyl-nonanol, 2,4,4-trimethyl-1-pentanol, 1-nonanol,
2-nonanol, 2,6-dimethyl-4-heptanol, 3,5,5-trimethyl-1-hexanol,
1-decanol, 2-decanol, 4-decanol, and 3,7-dimethyl-1-octanol;
alicyclic mono-alcohols such as cyclopentanol and cyclohexanol;
polyhydric alcohols such as ethylene glycol, propylene glycol,
1,4-butanediol, 1,4-dihydroxy-2-butene, 1,2-dihydroxy-3-butene, and
glycerin; ketones such as acetone, methyl ethyl ketone, methyl
butyl ketone, methyl isobutyl ketone, and methyl isopropyl ketone;
ethers such as dimethyl ether, diethyl ether, dipropyl ether,
methyl-tert-butyl ether, butyl ethyl ether, dibutyl ether, dipentyl
ether, tetrahydrofuran, and tetrahydropyran; esters such as methyl
acetate, ethyl acetate, isopropyl acetate, butyl acetate, methyl
acrylate, and methyl methacrylate; straight or branched aliphatic
saturated hydrocarbons such as n-pentane, n-hexane, methylpentane,
n-heptane, methylhexane, dimethylpentane, n-octane, methylheptane,
dimethylhexane, trimethylpentane, dimethylheptane, and n-decane;
straight or branched aliphatic unsaturated hydrocarbons such as
1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-heptene; aromatic
hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and
propylbenzene; alicyclic compounds such as cyclopentane,
methylcyclopentane, cyclohexane, methylcyclohexane,
dimethylcyclohexane, ethylcyclohexane, and propylcyclohexane;
halogen-containing solvents such as chloromethane, dichloromethane,
trichloromethane, tetrachloromethane, dichloroethylene,
trichloroethylene, and tetrachloroethylene; and nitriles such as
acetonitrile, propionitrile, butyronitrile, valeronitrile,
hexanenitrile, and benzonitrile. Among them, water, ketones,
ethers, esters, aliphatic saturated hydrocarbons, and
halogen-containing solvents are usable. Further, among them, water,
methyl ethyl ketone, dimethyl ether, diethyl ether, butyl acetate,
and hexane are preferable. The above-mentioned solvents may be used
alone or two or more of them may be used preferably while being
mixed. In addition, water to be used for the treatment with
activated carbon is preferably ultrapure water (ion resistance of
1.0 .OMEGA.cm or higher) treated by an ultrapure water apparatus
equipped with various kinds of filters such as a filter, an ion
exchange membrane and a reverse osmosis membrane.
The use amount of a solvent to be used for the treatment with
activated carbon is preferably not less than 10 parts by weight and
not more than 2000 parts by weight; more preferably not less than
100 parts by weight and not more than 1000 parts by weight; and
even more preferably not less than 200 parts by weight and not more
than 1000 parts by weight per 100 parts by weight of the crude
ionic compound. In the case the solvent amount is too high, the
reaction apparatus becomes large and it costs high and moreover,
the yield tends to be lowered and thus it is economically
disadvantageous. On the other hand, in the case the use amount of
the solvent is too low the purity of the ionic compound is
sometimes decreased. The ionic compound solution after the
treatment with activated carbon may be subjected as it is to the
treatment with an oxidizing agent.
As described above, it is one of preferred embodiments of the
invention that the crude ionic compound obtained in a syntesis is
subjected to the treatment with an oxidation agent and followed by
the treatment with activated carbon. Further, after the treatment
with an oxidizing agent, other refining methods described above may
be employed and it is preferable to carry out washing with water,
an organic solvent or their mixed solvent, or separatory
extraction.
A solvent to be used in this case is preferably a solvent which can
form 2-layer state with a solvent exemplified in the
above-mentioned treatment with activated carbon. For example, in
the case an organic solvent is used in the treatment with activated
carbon, water is preferable to be used for washing and separatory
extraction. Use of water makes it possible to efficiently extract
the alkali metal ion and the halide ion and remove these ionic
components from the ionic compound. Additionally, in terms of layer
separation from water and recovery efficiency of the ionic
compound, a combination of preferable extraction solvents include
combinations of water/hexane, water/methyl ethyl ketone,
water/methyl isobutyl ketone, water/dimethyl ether, water/diethyl
ether, water/ethyl acetate, water/butyl acetate, and
water/dichloromethane; and among them, more preferable combinations
are water/ethyl acetate, water/butyl acetate, water/methyl isobutyl
ketone, and water/diethyl ether, and even more preferable
combinations are water/ethyl acetate, water/butyl acetate, and
water/diethyl ether.
According to the invention employing the above-mentioned treatment
with an oxidizing agent, an ionic compound with a high purity and a
low content of impure ionic components is obtained.
<Uses>
The ionic compound Kt[B(CN).sub.4].sub.m of the invention has one
characteristic that it is in liquid-phase at 100.degree. C. or
lower and becomes an ionic liquid by selecting the cation
[Kt].sup.m+. Accordingly, the ionic compound of the invention
obtained by the above-mentioned production method is preferably
usable as a material composing electrochemical devices such as
primary batteries and batteries having charge/discharge mechanism,
e.g., lithium (ion) secondary batteries and fuel cells, and also
electrolytic capacitors, electric double layer capacitors, solar
cells, electrochromic display devices, and electrochemical gas
sensors.
Further, in general, since an ionic liquid has a characteristic
that it is a liquid having an ionic bond, it is known that the
ionic liquid has high electrochemical and thermal stability and
also has a property of selectively absorbing a specific gas such as
carbon dioxide, and the ionic compound obtained by the production
method of the invention also has characteristics same as described
above.
Consequently, as uses of the ionic compound of the invention other
than the above-mentioned electrochemical material uses, the ionic
compound can be used preferably for various uses, e.g., as a
repeatedly usable reaction solvent for organic synthesis and a
sealing agent and a lubricant for mechanical movable parts based on
the high thermal stability; as a conductivity supplying agent for
polymers based on both of the electrochemical property and thermal
stability; as a gas absorbent for carbon dioxide or the like based
on the gas-absorbing property; etc.
Next, a case of using the ionic compound of the invention as an
ion-conductive material for the above-mentioned electrochemical
devices will be described.
[Ion Conductive Material]
As described above, the ionic compound of the invention contains
tetracyanoborate defined by [B(CN).sub.4].sup.- as an anion and the
invention includes an ion-conductive material containing an ionic
compound having an anion defined by the following general formula
(XVI) other than the above-mentioned anion.
[Chemical Formula 24] (NC).sub.v--X.sup.d- (XVI) (in the formula
(XVI), X.sup.d denotes at least one element selected from Al, Si,
P, Ga, and Ge; and v is an integer of 4 to 6).
The ion-conductive material of the invention contains the ionic
compound having, as an anion component, tetracyanoborate or
tetracyanoborate together with an anion defined by the
above-mentioned general formula (XVI), and it is preferable that
the above-mentioned anion component has the highest occupied
molecular orbital energy level of -5.5 eV or lower which is
caluculated by employing a molecular orbital computation
method.
Investigations of an ion-conductive material by employing a
computational chemical technique are made in Journal of The
Electrochemical Society, 149 (12) A1572-A1577 (2002) and here, as
an index for obtaining a compound with high withstand voltage, the
highest occupied molecular orbital energy levels of various kinds
of anions are calculated by employing a molecular orbital
computation method. This document reports PF.sub.6.sup.- and
AsF.sub.6.sup.- as anions having low highest occupied molecular
orbital energy levels and wide potential windows. However,
compounds containing these anions have problems; that is, fluorine
atoms contained in the structure are isolated with lapse of time,
and corrode electrodes, or react on a trace of water contained in
the system and generate harmful hydrogen fluoride gas, or As itself
is toxic. On the other hand, the ionic compound of the invention
has a decreased content of impurities such as fluorine atoms as
described above and contains no As in the structure or in the
synthesis process, so that a problem of electrode corrosion or the
like is hardly caused. Further, the anion component of the
invention has the highest occupied molecular orbit energy level
same as those of PF.sub.6.sup.- and AsF.sub.6.sup.-, and has a wide
potential window, so that it can be used preferably as an ion
conductor.
In the above-mentioned formula (XVI), v is an integer of 4 to 6 and
determined based on the valence of the element X. For example, in
the case X is Al or Ga, v=4 and in the case X is Si or Ge, v=5.
Further, in the case X is P, v=6. A preferable embodiment of the
ion-conductive material of the invention has an ionic compound
having tetracyanoborate and/or the anion component defined by the
above-mentioned general formula (XVI) essentially. The anion
component is preferably tetracyanoborate and an anion defined by
the general formula (XVI) in which X is Al and v=4 and
tetracyanoborate is most preferable as the anion component.
The highest occupied molecular orbital energy level of the anion
component (tetracyanoborate and the anion component defined by the
general formula (XVI)) contained in the ion-conductive material of
the invention, which is calculated by employing a molecular orbital
computation method, is preferably -5.5 eV or lower, more preferably
-5.6 eV or lower, and even more preferably -5.7 eV or lower.
Further, in terms of corrosiveness and harmfulness, the
above-mentioned ion-conductive material is preferably those which
contain no F atom and no As in the composition. Furthermore, for
the same reason, the ion-conductive material is preferably those
which contain no Sb. In addition, the above-mentioned
ion-conductive material may contain only one kind of anion
component and also may contain two or more kinds of anion
components.
The cation contained in the ion-conductive material of the
invention is not particularly limited and may be either an organic
cation or an inorganic cation, as long as it can form a salt with
tetracyanoborate and the anion defined by the general formula
(XVI); however an onium cation is preferable. Examples of the onium
cation are onium cations defined by (III) to (V). In this case,
preferable uses of the ion-conductive material are electric double
layer capacitors, electrolytic capacitors, etc.
In the case the above-mentioned ion-conductive material is used as
a material of an electrolyte solution of an electric double layer
capacitor or an electrolytic capacitor, the amount of the
ion-conductive material is preferably 1 weight % or higher and 99.5
weight % or lower in 100 weight % of the material of an electrolyte
solution. It is more preferably 5 weight % or higher and 95 weight
% or lower and even more preferably 10 weight % or higher and 90
weight % or lower.
As described above, the ionic compound and the ion-conductive
material of the invention can work as an electrolyte composing an
electrolyte solution or a solid electrolyte in an ion conductor
which various kinds of electrochemical devices comprise. In
addition, these electrolyte solution and solid electrolyte may
contain other electrolyte salts in addition to the ion-conductive
material of the invention.
As other electrolyte salts, electrolytes containing ions as
carriers may be used, and one or more of electrolytes can be used.
It is preferable that the dissociation constant in an electrolyte
solution or a polymer solid electrolyte is high, and preferable
examples include alkali metal salts and alkaline earth metal salts
of trifluoromethane sulfonic acid such as LiCF.sub.3SO.sub.3,
NaCF.sub.3SO.sub.3, and KCF.sub.3SO.sub.3; alkali metal salts and
alkaline earth metal salts of perfluoroalkanesulfonic acid imide
such as LiC(CF.sub.3SO.sub.2).sub.3,
LiN(CF.sub.3CF.sub.2SO.sub.2).sub.2, and LiN(FSO.sub.2).sub.2;
alkali metal salts and alkaline earth metal salts of
hexafluorophosphoric acid such as LiPF.sub.6, NaPF.sub.6, and
KPF.sub.6; alkali metal salts and alkaline earth metal salts of
perchloric acid such as LiClO.sub.4 and NaClO.sub.4;
tetrafluoroboric acid salts such as LiBF.sub.4 and NaBF.sub.4;
alkali metals salts such as LiAsF.sub.6, LiI, NaI, NaAsF.sub.6, and
KI; quaternary ammonium salts of perchloric acid such as
tetraethylammonium perchlorate; quaternary ammonium salts of
tetrafluoroboric acid such as (C.sub.2H.sub.5).sub.4NBE.sub.4;
quaternary ammonium salts such as (C.sub.2H.sub.5).sub.4 NPF.sub.6;
and quaternary phosphonium salts such as (CH.sub.3).sub.4P BF.sub.4
and (C.sub.2H.sub.5).sub.4P BE.sub.4. Among them, alkali metal
salts and/or alkaline earth metal salts are preferable. Further, in
terms of solubility in an organic solvent or ion conductivity,
LiPF.sub.6, LiBF.sub.4, LiAsF.sub.6, alkali metal salts and
alkaline earth metal salts of perfluoroalkanesulfonic acid imide,
and quaternary ammonium salts are preferable. As the alkali metal
salts, lithium salts, sodium salts, and potassium salts are
preferable and as the alkaline earth metal salts, calcium salts and
magnesium salts are preferable. Lithium salts are more
preferable.
The used amount of above-mentioned other electrolytic salts is
preferably 0.1 weight % in the lower limit and 50 weight % in the
upper limit to the total 100 weight % of the ion-conductive
material of the invention and other electrolytic salts. If it is
less than 0.1 weight %, the absolute amount of ions may become
insufficient and ion conductivity may possibly become low and if it
exceeds 50 weight %, the mobility of ions may significantly be
inhibited. The upper limit is more preferably 30 weight %.
Uses of the ion-conductive material of the invention may be, for
example, for electrochemical devices such as electrolytic
capacitors, electric double layer capacitors, lithium ion
capacitors, solar cells, and electrochromic display devices besides
primary batteries and batteries having charge/discharge mechanism,
e.g., lithium (ion) secondary batteries and fuel cells. In general,
these devices have, as basic constituent elements, an ion
conductor, a negative electrode, a positive electrode, current
collectors, a separator, and a container.
As the above-mentioned ion conductor, a mixture of an electrolyte
and an organic solvent is preferable. If an organic solvent is
used, the ion conductor is called generally as an electrolyte
solution.
As the organic solvent, a non-protonic solvent in which the
above-mentioned ion-conductive material can be dissolved may be
used. The non-protonic solvent is preferably those having good
compatibility with the ion-conductive material of the invention and
high dielectric constant as well as high solubility for other
electrolytic salts, boiling point of 60.degree. C. or higher, and a
wide range of electrochemical stability. The non-protonic solvent
is more preferably organic solvents with low water content
(non-aqueous solvent). Examples of such solvent include ethers such
as 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran,
crown ether, triethylene glycol methyl ether, tetraethylene glycol
dimethyl ether, and dioxane; carbonates such as ethylene carbonate,
propylene carbonate, diethyl carbonate, and methyl ethyl carbonate;
aliphatic carbonic acid esters such as dimethyl carbonate, ethyl
methyl carbonate, diethyl carbonate, diphenyl carbonate, and methyl
phenyl carbonate; cyclic carbonate esters such as ethylene
carbonate, propylene carbonate, ethylene 2,3-dimethylcarbonate,
butylene carbonate, vinylene carbonate, and ethylene
2-vinylcarbonate; aliphatic carboxylic acid esters such as methyl
formate, methyl acetate, propionic acid, methyl propionate, ethyl
acetate, propyl acetate, butyl acetate, and amyl acetate; aromatic
carboxylic acid esters such as methyl benzoate and ethyl benzoate;
carboxylic acid esters such as .gamma.-butyrolactone,
.gamma.-valerolactone, and 8-valerolactone; phosphoric acid esters
such as trimethyl phosphate, ethyl dimethyl phosphate, diethyl
methyl phosphate, and triethyl phosphate; nitriles such as
acetonitrile, propionitrile, butyronitrile, valeronitrile,
hexanenitrile, benzonitrile, methoxypropionitrile, glutaronitrile,
adiponitrile, and 2-methylglutaronitrile; amides such as
N-methylformamide, N-ethylformamide, N,N-dimethylformamide,
N,N-dimethylacetamide, N-methylpyrrolidinone, N-methylpyrrolidone,
and N-vinylpyrrolidone; sulfur compounds such as dimethylsulfone,
ethylmethylsulfone, diethylsulfone, sulfolane, 3-methylsulfolane,
and 2,4-dimethylsulfolane; alcohols such as ethylene glycol,
propylene glycol, ethylene glycol monomethyl ether, and ethylene
glycol monoethyl ether; ethers such as ethylene glycol dimethyl
ether, ethylene glycol diethyl ether, 1,4-dioxane, 1,3-dioxolane,
tetrahydrofuran, 2-methyltetrahydrofuran,
2,6-dimethyltetrahydrofuran, and tetrahydropyrane; sulfoxides such
as dimethyl sulfoxide, methyl ethyl sulfoxide, and diethyl
sulfoxide; aromatic nitriles such as benzonitrile and tolunitrile;
nitromethane, 1,3-dimethyl-2-imidazolidinone,
1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone,
3-methyl-2-oxazolidinone, etc., and preferably these solvents can
be used individually or in combination. Among these solvents,
carbonic acid esters, aliphatic esters, and ethers are more
preferable; and carbonates such as ethylene carbonate, and
propylene carbonate, and .gamma.-butyrolactone,
.gamma.-valerolactone are even more preferable.
The concentration of the electrolyte in the above-mentioned ion
conductor is preferably 0.01 mol/dm.sup.3 or higher and not higher
than the saturated concentration. If it is lower than 0.01
mol/dm.sup.3, the ion conductivity is low and therefore, it is not
preferable. It is more preferably 0.1 mol/dm.sup.3 or higher and
2.5 mol/dm.sup.3 or lower.
In the case the ion-conductive material of the invention is used as
an electrolyte of a lithium ion battery, it is preferable to
dissolve the ion-conductive material in two or more kinds of
non-protonic solvents. In this case, it is preferable to prepare an
electrolyte solution by dissolving the ion-conductive material in a
mixed solvent of a non-protonic solvent with a dielectric constant
of 20 or higher and a non-protonic solvent with a dielectric
constant of 10 or lower among the above-mentioned organic
solvents.
In the case the ion-conductive material of the invention is
dissolved in the above-mentioned non-protonic solvent, for example,
propylene carbonate to obtain an electrolyte solution, the ion
conductivity at 25.degree. C. is preferably 0.5 mS/cm or higher in
a concentration of 1 mol/L. If the ion conductivity at 25.degree.
C. is lower than 0.5 mS/cm, the ion conductor obtained by using the
ion-conductive material of the invention is hard to keep excellent
ion conductivity for a long time and is difficult to work stably in
some cases. It is more preferably 1.0 mS/cm or higher.
The ion-conductive material of the invention is preferable to have
withstand voltage of 4 V to 500 V on the bases of Ag/Ag.sup.+. It
is more preferably 5 V to 500 V. As described above, it is possible
to show high withstand voltage by containing an anion having
highest occupied molecular orbital energy level of -5.5 eV or lower
calculated by employing the molecular orbital computation
method.
Hereinafter, (1) a lithium secondary battery, (2) an electrolyte
capacitor, (3) an electric double layer capacitor, and (4) a
lithium ion capacitor among the electrochemical devices using the
ion conductor of the invention will be described more in
detail.
(1) Lithium Secondary Battery
A lithium secondary battery comprises a positive electrode, a
negative electrode, a separator inserted between the positive
electrode and the negative electrode, and an ion conductor obtained
by using the ion-conductive material of the invention as basic
constituent elements. In this case, the material for an electrolyte
solution of the invention contains a lithium salt as an
electrolyte. Such a lithium secondary battery is preferably a
non-aqueous electrolytic lithium secondary battery, which is a
lithium secondary battery containing an electrolyte other than a
water-based electrolyte. This lithium secondary battery employs
coke as a negative electrode active material and a Co-containing
compound as a positive electrode active material, and in this
lithium secondary battery, at the time of charge, reaction of
C.sub.6Li.fwdarw.6C+Li+e is caused at the negative electrode and
the electrons (e) generated on the negative electrode surface are
transferred to the positive electrode surface in the electrolyte
solution by ion conduction, and reaction of
CoO.sub.2+Li+e.fwdarw.LiCoO.sub.2 is caused at the positive
electrode surface, and thus electric current flows from the
negative electrode to the positive electrode. At the time of
discharge, reverse reactions of the reactions at the time of charge
are caused and electric current flows from the positive electrode
to the negative electrode. In such a manner, electricity is stored
or supplied by chemical reactions of ions.
For the above-mentioned negative electrode, conventionally known
materials to be used for the negative electrode can be employed
without any particular limit and usable examples are carbon
materials such as graphite, e.g. natural graphite and artificial
graphite, coke, and charcoal of organic material; lithium alloys
such as lithium-aluminum alloys, lithium-magnesium alloys,
lithium-indium alloys, lithium-thallium alloys, lithium-lead
alloys, and lithium-bismuth alloys; and metal oxides and metal
sulfides containing one or more of titanium, tin, iron, molybdenum,
niobium, vanadium, zinc, etc. Among these substances, metal lithium
and carbon materials which can absorb and desorb alkali metal ion
are more preferable.
For the above-mentioned positive electrode, conventionally known
materials to be used for the positive electrode can be employed
without any particular limit and usable examples are
lithium-containing transition metal oxides such as LiCoO.sub.2,
LiMnNO.sub.2, LiFeO.sub.2, and LiFePO.sub.4. The average particle
diameter of the positive electrode active material particles is
preferably 0.1 to 30 .mu.m.
(2) Electrolytic Capacitor
An electrolytic capacitor comprises a positive electrode foil, a
negative electrode foil, a sheet of electrolytic paper as a
separator inserted between the positive electrode foil and the
negative electrode foil, lead wires, and an ion conductor obtained
by using the ion-conductive material of the invention as basic
constituent elements. As such an electrolytic capacitor, an
aluminum electrolytic capacitor is preferable. Such an aluminum
electrolytic capacitor is preferably those containing, as a
dielectric, a thin oxide coating (aluminium oxide) formed on the
surface of an aluminum foil by electrolytic anodization, which is
previously surface-roughened to form fine unevenness by
electrolytic etching.
(3) Electric Double Layer Capacitor
An electric double layer capacitor comprises a negative electrode,
a positive electrode and an ion conductor obtained by using the
ion-conductive material of the invention as a basic constituent
part and a preferable embodiment is those obtained by involving an
electrolyte solution which is the ion conductor into electrode
parts composed of a positive electrode and a negative electrode set
face to face.
Preferable examples of the above-mentioned negative electrode are
activated carbon, porous metal oxides, porous metals, and
conductive polymers. Preferable examples of the above-mentioned
positive electrode are activated carbon, porous metal oxides,
porous metals, and conductive polymers.
(4) Lithium Ion Capacitor
A lithium ion capacitor is a capacitor based on the principle of a
common electric double layer capacitor and using a carbon-based
material capable of absorbing lithium ion as a negative electrode
material, and is provided with improved energy density by adding
lithium ion thereto, and has a structure formed by combining the
negative electrode of a lithium ion secondary battery, and the
positive electrode of an electric double layer capacitor based on
different principles of charge and discharge for the positive
electrode and the negative electrode.
Materials for the above-mentioned negative electrode are preferably
those which can absorb and desorb lithium ions. Preferable examples
of the materials which can absorb and desorb lithium ions are
thermally decomposed carbon; coke such as pitch coke, needle coke,
and petroleum coke; graphite; glassy carbon; calcined organic
polymer, which are obtained by calcining and carbonizing phenol
resins, furan resins, and the like at a proper temperature; carbon
fibers; carbon materials such as activated carbon; polymers such as
polyacetylene, polypyrrole, and polyacene; lithium-containing
transition metal oxides or transition metal sulfides such as
Li.sub.4/3Ti.sub.5/3O.sub.4 and TiS.sub.2; metals to be alloyed
with alkali metals such as Al, Pb, Sn, Bi, and Si; cubic system
intermetallic compounds having lattices in which alkali metals are
intercalated such as AlSb, Mg.sub.2Si, and NiSi.sub.2; and
lithium-nitrogen compounds such as Li.sub.34G.sub.fN (G: a
transition metal; f: a real number exceeding 0 and lower than 0.8).
One or more of these substances may be used. Among these
substances, carbon materials are more preferable.
On the other hand, as the positive electrode, activated carbon,
porous metal oxides, porous metals, and conductive polymers are
preferable. The ion conductor using the ion-conductive material of
the invention forms the electrolyte solution put between the
negative electrode and the positive electrode.
EXAMPLES
Hereinafter, the invention will be described more concretely with
reference to Examples. However, it is not intended that the
invention be limited to the illustrated Examples. Modifications and
substitutions to specific process conditions and structures can be
made without departing from the spirit and scope of the present
invention.
[NMR Measurement]
.sup.1H-NMR and .sup.13C-NMR spectra were measured by using "Unity
Plus" (400 MHz) manufactured by Varian and based on the peak
intensity of proton and carbon, the structure of each sample was
analyzed. "Advance 400 M" (400 MHz) manufactured by Bruker was
employed for .sup.11B--NMR spectra measurement.
The content of impurities containing F atom was measured by the
following method. Using d6-DMSO as a solvent, .sup.11B--NMR
measurement was carried out. The area of a peak derived from
B(CN).sub.4 at -38 ppm in the obtained .sup.11B--NMR spectrum was
defined as 100 mol % and this area of the peak and the area of
another peak (derived from an impurity) were compared relatively to
calculate the number of moles of the impurity (mol percentage (mol
%)).
[Measurement of Ion Conductivity]
Each ionic compound obtained in the following Examples was
dissolved in .sub.7-butyrolactone (GBL) to produce an ionic
compound solution of 35 weight % concentration.
Using an impedance analyzer ("SI 1260" manufactured by Solartron)
and a SUS electrode, the ion conductivity of the ionic compound
solution was measured at a temperature of 25.degree. C. by a
complex impedance method.
[Measurement of Potential Window]
A 35 weight % ionic compound solution was prepared in the same
manner as that in the ion conductivity measurement.
In 25.degree. C. ambient atmosphere, the potential window was
measured by a cyclic voltammetry tool ("HSV-100", manufactured by
Hokuto Denko Corporation) using a tripolar cell as an electrode. A
glassy carbon electrode is used for a working electrode in the
tripolar cell; a Pt electrode for an objective electrode; and an Ag
electrode for a reference electrode.
[Measurement of Thermal Decomposition Starting Temperature 1]
In an aluminum pan, 10 mg of each ionic compound obtained by the
following Synthesis Example was put and elevated temperature at
5.degree. C./min and the temperature when the weight was decreased
by 2% from the initial weight was measured with a thermo gravimetry
differential thermal analyzer ("EXSTAR 6000 TG/DTA"; manufactured
by Seiko Instrument Inc.).
Example 1
In Example 1, a tetracyanoborate-containing ionic compound was
synthesized using a cyanide M.sup.a(CN).sub.n as a starting
material.
Synthesis Example 1-1:
Synthesis of Tetrabutylammonium Tetracyanoborate (Bu.sub.4NTCB)
A 50 ml flask equipped with a stirring device, a dripping funnel,
and a reflux tube was purged with nitrogen and under nitrogen
atmosphere at room temperature, 5.1 g (15.8 mmol) of
tetrabutylammonium bromide, 9.26 g (78.9 mmol) of zinc (II)
cyanide, 10 ml of toluene and 2.8 g (11.2 mmol) of boron tribromide
were added and thereafter, the contents were stirred for 2 days
while being heated in an oil bath at 130.degree. C. After 2 days,
toluene was removed from the flask in reduced pressure to obtain a
black solid. After pulverized with a mortar, the obtained solid was
put in a beaker equipped with stirring device and 200 ml of
chloroform was added twice to extract the product to the chloroform
layer. Next, the obtained chloroform solution was transferred to a
separatory funnel and washed with 200 ml of water and thereafter,
an organic layer was separated and concentrated by an evaporator to
obtain an oily crude product. The crude product was refined by
column chromatography filled with neutral alumina (developing
solvent, a mixed solution of diethyl ether and chloroform) and a
fraction containing the product was separately obtained and dried
by removing the solvent to obtain tetrabutylammonium
tetracyanoborate, as a product (yellow solid, produced amount: 1.4
g (3.9 mmol), yield: 35%, melting point: 90.degree. C.).
.sup.1H-NMR (d6-DMSO): .delta. 3.16 (m, 8H), 1.56 (m, 8H), 1.30
(ddq, J=11 Hz, J=11 Hz, J=7.2 Hz, 8H), 0.92 (t, J=7.2 Hz, 12H)
.sup.13C-NMR (d6-DMSO): .delta. 121.9 (m), 57.7 (s), 39.1 (s), 19.4
(s), 13.7 (s) .sup.11B--NMR (d6-DMSO) .delta. -39.6 (s)
Synthesis Example 1-2
Synthesis of 1-ethyl-3-Methylimidazolium Tetracyanoborate
EtMeImTCB)
The same operation as that of Synthesis Example 1-1 was carried out
except that 3.0 g (15.8 mmol) of 1-ethyl-3-methylimidazolium
bromide was used in place of tetrabutylammonium bromide to obtain
1-ethyl-3-methylimidazolium tetracyanoborate (yellow oily material,
produced amount: 1.0 g (4.4 mmol), yield: 38%, melting point:
15.degree. C.). .sup.1H-NMR (d6-DMSO) .delta. 8.41 (s, 1H), 7.34
(d, J=21.6 Hz, 2H), 3.81 (s, 3H), 1.45 (t, J=7.2 Hz, 3H)
.sup.13C-NMR (d6-DMSO) .delta. 136.5 (s), 132.2 (m), 122.9 (s),
45.8 (s), 36.8 (s), 15.4 (s) .sup.11B--NMR (d6-DMSO) .delta. -39.6
(s)
Synthesis Example 1-3
Synthesis of Triethylammonium Tetracyanoborate (Et.sub.3HNTCB)
The same operation as that of Synthesis Example 1-1 was carried out
except that 2.9 g (15.8 mmol) of triethylammonium bromide was used
in place of tetrabutylammonium bromide to obtain triethylammonium
tetracyanoborate (yellow solid, produced amount: 1.0 g (4.5 mmol),
yield: 40%, melting point: 150.degree. C.). .sup.1H-NMR (d6-DMSO)
.delta. 8.83 (s, 1H), 3.10 (q, J=7.2 Hz, 6H), 1.17 (t, J=7.2 Hz,
9H) .sup.13C-NMR (d6-DMSO) .delta. 121.9 (m), 46.0 (s), 8.8 (s)
.sup.11B--NMR (d6-DMSO) .delta. -39.6 (s)
Synthesis Example 1-4
Synthesis of Triethylmethylammonium Tetracyanoborate
(ET.sub.3MeNTCB)
The same operation as that of Synthesis Example 1-1 was carried out
except that 3.1 g (15.8 mmol) of triethymethyllammonium bromide was
used in place of tetrabutylammonium bromide to obtain
triethylmmethylammonium tetracyanoborate (yellow solid, produced
amount: 1.2 g (5.0 mmol), yield: 45%, melting point: 115.degree.
C.). .sup.1H-NMR (d6-DMSO) .delta. 3.23 (q, J=6.8 Hz, 6H), 2.86 (s,
3H), 1.18 (t, J=6.8 Hz, 9H) .sup.13C-NMR (d6-DMSO) .delta. 122.5
(m), 55.2 (s), 46.2 (s), 7.7 (s) .sup.11B--NMR (d6-DMSO) .delta.
-39.6 (s)
Synthesis Example 1-5
Synthesis of Tetraethylammonium Tetracyanoborate (Et.sub.4NTCB)
The same operation as that of Synthesis Example 1-1 was carried out
except that 3.3 g (15.8 mmol) of tetraethylammonium bromide was
used in place of tetrabutylammonium bromide to obtain
tetraethylammonium tetracyanoborate (yellow solid, produced amount:
1.1 g (4.5 mmol), yield: 40%). .sup.1H-NMR (d6-DMSO) .delta. 3.21
(q, J=7.4 Hz, 8H), 1.50 (tt, J=7.4 Hz, 12H) .sup.13C-NMR (d6-DMSO)
.delta. 121.9 (m), 51.5 (s), 7.4 (s) .sup.11B--NMR (d6-DMSO)
.delta. -39.6 (s)
Synthesis Example 1-6
Synthesis of Tetrabutylammonium Tetracyanoborate (Et.sub.4NTCB)
The same operation as that of Synthesis Example 1-1 was carried out
except that 4.4 g (15.8 mmol) of tetraethylammonium chloride was
used in place of tetrabutylammonium bromide to obtain
tetraethylammonium tetracyanoborate (yellow solid, produced amount:
1.6 g (4.5 mmol), yield: 40%, melting point: 90.degree. C.).
The product showed an NMR spectrum and various physical properties
similar to those of the product of Synthesis Example 1-1.
Synthesis Example 1-7
Synthesis of Tetrabutylammonium Tetracyanoborate (Bu.sub.4NTCB)
A 50 ml flask equipped with a stirring device, a dripping funnel,
and a reflux tube was purged with nitrogen and under nitrogen
atmosphere at room temperature, 5.1 g (15.8 mmol) of
tetrabutylammonium bromide, 9.26 g (78.9 mmol) of zinc (II) cyanide
and 11.2 ml (11.2 mmol) of a p-xylene solution of 1.0 M boron
trichloride were added and thereafter, the contents were stirred
for 2 days while being heated in an oil bath at 150.degree. C.
After 2 days, the organic solvent was removed from the flask in
reduced pressure to obtain a black solid. After pulverized with a
mortar, the obtained solid was put in a beaker equipped with
stirring device and 200 ml of chloroform was added twice to extract
the product to the chloroform layer. Next, the obtained chloroform
solution was transferred to a separatory funnel and washed with 200
ml of water and thereafter, an organic layer was separated and
concentrated by an evaporator to obtain an oily crude product. The
crude product was refined by column chromatography filled with
neutral alumina (developing solvent, a mixed solution of diethyl
ether and chloroform) and a fraction containing the product was
separately obtained and dried by removing the solvent to obtain
tetrabutylammonium tetracyanoborate, as a product (yellow solid,
produced amount: 2.4 g (6.8 mmol), yield: 61%, melting point:
90.degree. C.).
The product showed an NMR spectrum and various physical properties
similar to those of the product of Synthesis Example 1-1.
Synthesis Example 1-8
A 100 ml three-neck flask equipped with a stirring device, a
dripping funnel, and a reflux tube was loaded with 10.4 g (160
mmol) of potassium cyanide, 10.2 g (32 mmol) of tetrabutylammonium
bromide, 5.7 g (22.7 mmol) of boron tribromide, and 18.9 g (205
mmol) of toluene at room temperature, and thereafter, the contents
were stirred for 7 days while being heated and refluxed in an oil
bath at 130.degree. C. After 7 days, toluene was removed from the
flask in reduced pressure and 100 ml of chloroform was added
thereto and stirred for 30 minutes at room temperature. Next, after
the solution was filtered to remove the precipitate, the filtrate
was concentrated to obtain an oily crude product. The crude product
was refined by column chromatography filled with neutral alumina
(developing solvent, diethyl ether: chloroform=1:1 (vol. ratio)).
However, it was found that tetrabutylammonium tetracyanoborate was
not at all produced and tetrabutylammonium bromide, a starting
material, remained.
Further, the above-mentioned precipitate and the refined product
were analyzed by .sup.11B--NMR to find no peak derived from
tetracyanoborate.
The same reaction was tried by changing the reaction container to a
sealed pressure resistant container (capacity: 100 ml, inner
cylinder of Teflon (registered trade name), made of stainless
steel), however, no product was obtained.
The respective various physical properties of the ionic compounds
obtained by the respective Synthesis Examples were measured by the
above-mentioned measurement methods and the results are shown in
Table 1.
TABLE-US-00001 TABLE 1 Thermal .gamma.- decom- Butyro- Ion position
lactone conduc- starting Compound (part tivity temper Potential
(part by by (S/cm) ature window mass) mass) (25.degree. C.)
(.degree. C.) (V) Synthesis Bu.sub.4NTCB 65 0.009 210 -3.2~+2.0
Example 1-1 35 Synthesis EMImTCB 65 0.021 330 -2.4~+2.0 Example 1-2
35 Synthesis Et.sub.3HNTCB 65 0.018 285 -1.7~+2.0 Example 1-3 35
Synthesis Et.sub.3MeNTCB 65 0.018 280 -3.0~+2.0 Example 1-4 35
Synthesis Et.sub.4NTCB 65 0.015 220 -3.0~+2.0 Example 1-5 35
From the above-mentioned results, according to the first production
method of the invention, reaction was promoted at a lower
temperature (130.degree. C. to 150.degree. C.) than that in the
case of using an alkali metal cyanide (reaction temperature:
250.degree. C.). Further, without using costly trimethylsilyl
cyanide, a tetracyanoborate-containing ionic compound could bewas
obtained stably.
Experiment Examples 1 to 2 and Comparative Experiment Examples 1 to
4
The thermal decomposition starting temperature was measured for
mixtures containing 1-ethyl-3-methylimidazolium tetracyanoborate
synthesized in Synthesis Example 1-2 and mixtures containing
1-ethyl-3-methylimidazolium tetrafluoroborate (EtMeImBF.sub.4), as
an impurity (for organic synthesis, made available by Wako Pure
Chemical Industries, Ltd.), in the mixing ratio compositions shown
in the following Table 2. The measurement was carried out by the
following measurement 2 of thermal decomposition starting
temperature. The results are shown in Table 2.
[Measurement of Thermal Decomposition Starting Temperature 2]
In an aluminum pan, 5 mg of each ionic compound having a
composition shown in the following Table 2 was put and elevated
temperature at 10.degree. C./min to 230.degree. C. and at
0.5.degree. C./min from 230.degree. C. to 350.degree. C. and the
temperature when the weight was decreased by 2% from the initial
weight was measured with a thermo gravimetry differential thermal
analyzer ("EXSTAR 6000 TG/DTA", manufactured by Seiko Instrument
Inc.).
TABLE-US-00002 TABLE 2 EMeIm EMeIm Thermal B(CN).sub.4 BF.sub.4
decomposition starting (mol %) (mol %) temperature (.degree. C.)
Experiment 100 0 304 Example 1 Experiment 97 3 289 Example 2
Comparative 95 5 276 Experiment Example 1 Comparative 90 10 265
Experiment Example 2 Comparative 75 25 262 Experiment Example 3
Comparative 50 50 261 Experiment Example 4
From Table 2, it can be understood that as the content of fluorine
atom-containing impurities was increased, the thermal decomposition
starting temperature was deceased and in the case fluorine
atom-containing impurities were contained in the ionic compound,
the physical property (heat resistance) of the ionic compound was
deteriorated.
Further, it can be understood that the thermal decomposition
starting temperature of Comparative Experimental Example 1 was
lower by no less than 20.degree. C. as compared with that of
Experimental Example 1 and when the content of F atom-containing
impurities exceeds 5 mol %, the material durability under high
temperature condition was considerably deteriorated. It is
supposedly attributed to that the impurities having B--F bond and
contained in the ionic compound were reacted with oxygen atoms of
water and oxygen existing in air and decomposed.
In Experimental Examples 1 and 2 having the content of F
atom-containing impurities of 3 mol % or lower, decrease of the
thermal decomposition starting temperature was little. Further,
from the results of Table 1, it can be understood the product is
preferably usable as an electrolytic solution material.
Experimental Example 3
A resin composition was obtained by adding 10 parts by weight of
1-ethyl-3-methylimidazolium tetracyanoborate as a conductivity
supplying agent to 90 parts by weight of hydrogen-terminated
ethylene oxide/propylene oxide copolymer and heating and kneading
the mixture at 70.degree. C.
Next, 20 parts by weight of the obtained resin composition was
added to 100 parts by weight of a methyl methacrylate polymer
(molecular weight; about 200,000), which is a thermoplastic resin,
and the mixture was heated and kneaded at 100.degree. C. by a test
roll apparatus ("HR-2 model", manufactured by Nisshin Kagaku Inc.)
to obtain a sheet having an even thickness of 2 mm.
When the surface resistance of the obtained sheet was measured by a
surface resistance measurement device ("HT-210", manufactured by
Mitsubishi Chemical Corporation), it was 9.times.10.sup.7.OMEGA..
No ionic compound bleeding was observed.
From the results of Experimental Example 3, it is found that the
ionic compound of the invention could be used preferably as a
conductivity supplying agent.
Experimental Example 4
The flow point, dynamic viscosity, and friction coefficient of
1-ethyl-3-methylimidazolium tetracyanoborate synthesized in
Synthesis Example 1-2 were evaluated.
The flow point was evaluated according to JIS K2269-1987. The
observed flow point of EtMeImTCB was -20.degree. C. The dynamic
viscosity was evaluated according to JIS K2283-2000. The dynamic
viscosity of EtMeImTCB at 40.degree. C. was 30 cSt
(3.0.times.10.sup.-5m.sup.2/s). The friction coefficient was
measured by a pendulum-type friction tester ("Soda pendulum-type
oiliness friction tester" manufactured by Shinko Engineering Co.,
Ltd.). The friction coefficient of EtMeImTCB was 0.16.
From the results of Experimental Example 4, it can be understood
that the ionic compound of the invention had fluidity even in low
temperature environments and also a low friction coefficient and
thus was suitable as a lubricant.
Since the content of F atoms and impurities containing F atom was
lowered to an extremely low level in the ionic compound of the
invention, in the case of being used for various kinds of
applications, the ionic compound exerts stable characteristics
(thermal, physical, and electrochemical characteristics) without
causing a problem such as corrosion of peripheral members.
Example 2
In Synthesis Example 2, an ionic compound having tetracyanoborate
as an anion was synthesized by using an ammonium cyanide compound
as a starting material.
Raw Material Synthesis: Ammonium Cyanide Synthesis 1
To a 2 L flask equipped with a stirring device, and a dripping
funnel, 200 ml of methylene chloride and 67.6 g (200 mmol) of
tetrabutylammonium sulfoxide were added and stirred, then, 50 ml of
an aqueous 4 M NaOH solution was added to the resulting solution
and stirred. After 10 g (204 mmol) of sodium cyanide previously
dissolved in 20 ml of water was dropwise added through a dripping
funnel to the obtained methylene chloride solution, the mixed
solution was stirred for 30 minutes at room temperature (25.degree.
C.). The obtained suspension was filtered and the filtrate was
concentrated to obtain 58.7 g of oily crude tetrabutylammonium
cyanide.
Synthesis Example 2-1
Tetrabutylammonium Tetracyanoborate (Bu.sub.4NTCB) Synthesis 1
After a 50 ml flask equipped with a stirring device, a dripping
funnel, and a reflux condenser was purged with nitrogen, and under
nitrogen atmosphere at room temperature 0.64 g (2.0 mmol) of
tetrabutylammonium bromide, 2.65 g (9.9 mmol) of tetrabutylammonium
cyanide, 0.35 g (1.4 mmol) of boron tribromide, and 1.4 ml of
toluene were added, the contents were stirred for 2 days while
being heated in an oil bath at 130.degree. C. After 2 days, toluene
was removed from the flask in reduced pressure to obtain a black
solid.
The black solid was put in a beaker equipped with a stirring
device, 100 ml of chloroform and 100 ml of water were added
thereto, the chloroform layer was extracted by a separatory funnel
and the chloroform layer was washed separately with 100 ml of water
twice, and thereafter, the chloroform layer was concentrated in
reduced pressure to obtain an oily crude product. The crude product
was refined by column chromatography filled with neutral alumina
(developing solvent, a mixed solution of diethyl ether and
chloroform) and a fraction containing the product was separately
obtained and dried by removing the solvent to obtain
tetrabutylammonium tetracyanoborate, as a product (yellow solid,
produced amount: 0.39 g (1.4 mmol), yield: 77%, melting point:
90.degree. C.).
The respective various physical properties of the obtained
tetrabutylammonium tetracyanoborate, which is an ionic compound,
were measured by the above-mentioned measurement methods and the
results are shown as follows. The product showed an
NMR spectrum same as that of the product of Synthesis Example
1-1.
Ion conductivity (25.degree. C.): 0.009 S/cm
Thermal decomposition starting temperature: 210.degree. C.
Potential Window: -3.2 V to 2.0 V .sup.1H-NMR (d6-DMSO):
.delta.3.16 (m, 8H), 1.56 (m, 8H), 1.30 (ddq, J=11 Hz, J=11 Hz,
J=7.2 Hz, 8H), 0.92 (t, J=7.2 Hz, 12H) .sup.13C-NMR (d6-DMSO):
8121.9 (m), 57.7 (s), 39.1 (s), 19.4 (s), 13.7 (s) .sup.11B--NMR
(d6-DMSO): .delta.-39.6 (s)
Synthesis Example 2-2
Tetrabutylammonium Tetracyanoborate Synthesis 2
The same operation as that of Synthesis Example 2-1 was carried
out, except that 1.4 ml (1.4 mmol, 1 M-p-xylene solution,
manufactured by Aldrich) of boron trichloride was used in place of
boron tribromide and no toluene was used to obtain
tetrabutylammonium tetracyanoborate, as a product (yellow solid,
produced amount: 0.21 g (0.6 mmol), yield: 42%, melting point:
90.degree. C.).
The product showed an NMR spectrum and various physical properties
similar to those of the product of Synthesis Example 2-1.
Synthesis Example 2-3
Tetrabutylammonium Tetracyanoborate Synthesis 3
The same operation as that of Synthesis Example 2-2 was carried
out, except that no tetrabutylammonium bromide was used to obtain
tetrabutylammonium tetracyanoborate, as a product (yellow solid,
produced amount: 0.18 g (0.5 mmol), yield: 35%, melting point:
90.degree. C.).
The product showed an NMR spectrum and various physical properties
similar to those of the product of Synthesis Example 2-1.
Synthesis Example 2-4
Tetrabutylammonium tetracyanoborate (Bu.sub.4NTCB) synthesis 4
After a 50 ml flask equipped with a stirring device, a dripping
funnel, and a reflux condenser was purged with nitrogen, and under
nitrogen atmosphere at room temperature 0.64 mg (2.0 mmol) of
tetrabutylammonium bromide, 1.65 g (6.2 mmol) of tetrabutylammonium
cyanide, 0.20 g (1.4 mmol) of triethyl borate, and 1.4 ml of
dimethylsulfoxide were added, the contents were stirred for 2 days
while being heated in an oil bath at 170.degree. C. After 2 days,
the organic solvent was removed from the flask in reduced pressure
to obtain a black solid.
The black solid was put in a beaker equipped with a stirring
device, 100 ml of chloroform and 100 ml of water were added
thereto, the chloroform layer was extracted by a separatory funnel
and the chloroform layer was washed separately with 100 ml of water
twice, and thereafter, the chloroform layer was concentrated in
reduced pressure to obtain an oily crude product. The crude product
was refined by column chromatography filled with neutral alumina
(developing solvent: a mixed solution of diethyl ether and
chloroform) and a fraction containing the product was separately
obtained and dried by removing the solvent to obtain
tetrabutylammonium tetracyanoborate, as a product (yellow solid,
produced amount: 0.1 g (0.3 mmol), yield: 20%, melting point:
90.degree. C.).
The product showed an NMR spectrum and various physical properties
similar to those of the product of Synthesis Example 2-1.
Synthesis Example 2-5
Tetrabutylammonium Tetracyanoborate Synthesis 5
After a 2 L flask equipped with a stirring device, a dripping
funnel, and a reflux condenser was loaded with 58.7 g of un-refined
tetrabutylammonium cyanide obtained by raw material synthesis and
11.6 g (36.3 mmol) of tetrabutylammonium bromide and purged with
nitrogen, 26 ml (26 mmol) of a p-xylene solution of 1 M boron
trichloride was dropwise added to the flask through a dripping
funnel at room temperature. While being heated at 150.degree. C.,
the reaction solution was stirred for 2 days and thereafter, the
solvent was removed and the obtained residue was refined by column
chromatography using neutral alumina as a packing material
(developing solvent: a mixed solvent obtained by mixing
dichloroethane and diethyl ether at 1:1 (vol. ratio)) to obtain
tetrabutylammonium tetracyanoborate (produced amount: 3.2 g (9
mmol), yield: 35%).
The product showed an NMR spectrum and various physical properties
similar to those of the product of Synthesis Example 2-1.
Synthesis Example 2-6
Tetrabutylammonium Tetracyanoborate Synthesis 6
After a 50 ml flask equipped with a stirring device, a dripping
funnel, and a reflux condenser was purged with nitrogen, and under
nitrogen atmosphere and at room temperature, 0.65 g (2.0 mmol) of
tetrabutylammonium bromide, 2.98 g (11.0 mmol) of
tetrabutylammonium cyanide, and 2.0 ml (2.0 mmol) of a p-xylene
solution of 1 M boron trichloride were added, the contents were
stirred for 2 days while being heated in an oil bath at 150.degree.
C. Thereafter, the solvent was removed to obtain a black solid.
The obtained crude product was made to be an ethyl acetate solution
of 10 wt % and mixed with 2.1 g of activated carbon (Carborafin
(registered trade name)-6 manufactured by Japan EnviroChemicals,
Ltd.) and stirred for 30 minutes at room temperature. Thereafter,
the obtained activated carbon suspension was filtered with a
membrane filter (0.2 .mu.m, made of PTFE, hydrophilic), operation
involving dispersing activated carbon on the filter in 6.5 g of
ethyl acetate, stirring the obtained dispersion at 50.degree. C.
for 10 minutes and filtering the dispersion again was repeated 5
times. Obtained filtrate and washing solution were mixed and dried
by removing the solvent to obtain brown solid.
Next, the obtained brown solid was mixed with 0.7 g of hydrogen
peroxide (aqueous 30 wt % solution) and stirred for 60 minutes at
50.degree. C. After 3 g of butyl acetate was added to the obtained
solution and stirred for 30 minutes at room temperature to produce
dispersion state, the dispersion was transferred to a container for
centrifugal separation and then the container was shaken for 90
seconds and subjected to centrifugal separation (1700 rpm, 10
minutes). Thereafter, the upper layer (butyl acetate layer) was
concentrated and obtained light yellow solid was coarsely dried for
30 minutes at 80.degree. C. in reduced pressure and the crude
product was pulverized with a mortar to obtain a powder. The powder
was spread on a tray and further dried for 3 days at 80.degree. C.
in reduced pressure to obtain tetrabutylammonium tetracyanoborate,
a desired product, (produced amount 0.36 g (1.0 mmol), yield
50%).
The product showed an NMR spectrum and various physical properties
similar to those of the product of Synthesis Example 2-1.
Synthesis Example 2-7
Triethylmethylammonium Tetracyanoborate Synthesis
The same operation as that of Synthesis Example 2-6 was carried
out, except that 1.5.6 g (11 mmol) of triethylmethylammonium
cyanide was used in place of tetrabuthylammonium cyanide and no
tetrabuthylammonium bromide was used to obtain
triethylmethylammonium tetracyanoborate(Et.sub.3MeNTCB), as a
product (light yellow solid, produced amount: 0.23 g (1 mmol),
yield: 50%, melting point: 115.degree. C.). The product showed an
NMR spectrum and various physical properties similar to those of
the product of Synthesis Example 1-4.
According to the second production method of the invention, the
ionic compound having tetracyanoborate can be produced in reaction
temperature condition of 200.degree. C. or lower. Further, without
using costly trimethylsilane cyanide, the ionic compound having
tetracyanoborate is obtained.
Example 3
In Example 3, an ionic compound having tetracyanoborate was
synthesized by using an trimethylsilyl cyanide as a starting
material.
Synthesis Example 3-1
Triethylmethylammonium Tetracyanoborate (Et.sub.3MeNTCB) Synthesis
1
To a 1 L eggplant flask equipped with a stirring device, a reflux
condenser, a discharge device, and dripping funnel, 30.3 g (200
mmol) of previously heated and dried triethylmethylammonium
chloride (Et.sub.3MeNCl) was added. After the container was purged
with nitrogen, 109.0 g (1100 mm) of trimethylsilyl cyanide (TMSCN)
was added at room temperature and stirred and mixed. Next, 200 mL
(200 mmol) of a p-xylene solution of 1 mol/L boron trichloride was
gradually and dropwise added through the dripping funnel. On
completion of the dropwise addition, the reaction container was
heated to 150.degree. C. and reaction was carried out while
trimethylsilyl chloride (TMSCl, boiling point: about 57.degree. C.)
generated as a byproduct being discharged through a reflux
discharge part.
After 30 hour heating and stirring, the inside pressure of the
reaction container was reduced by a diaphragm pump and a p-xylene
solution of TMSCN was removed through the reflux discharge part.
Thereafter, 45 g of the crude product and 225 g of ethyl acetate
were put in a 500 mL beaker equipped with a stirring device and
stirred for 5 minutes for dissolution and 135 g of activated carbon
(Carborafin (registered trade name)-6 manufactured by Japan
EnviroChemicals, Ltd.) was added thereto and stirred for 10
minutes. The obtained activated carbon suspension was filtered with
a membrane filter (0.2 .mu.m, made of PTFE) and the solvent was
removed and obtained product was dried to obtain
triethylmethylammonium tetracyanoborate, an desired product, (light
yellow solid) (produced amount: 37.9 g (164 mmol), yield: 82%,
melting point: 115.degree. C.).
The various physical properties of the obtained
triethylmethylammonium tetracyanoborate were measured by the
above-mentioned measurement methods. The results are as
follows.
Ion conductivity (25.degree. C.): 0.018 S/cm
Thermal decomposition starting temperature: 280.degree. C.
Potential window: -3.2 V to 2.0 V .sup.1H-NMR(d6-DMSO) .delta.
3.23(q,J=6.8 Hz,6H), 2.86(s,3H), 1.18(t,J=6.8 Hz,9H)
.sup.13C-NMR(d6-DMSO) .delta. 112.5(m), 55.2(s), 46.2(s), 7.7(s)
.sup.11B--NMR(d6-DMSO) .delta. -39.6(s)
Synthesis Example 3-2
Triethylmethylammonium Tetracyanoborate Synthesis 2
Triethylmethylammonium tetracyanoborate (liquid yellow solid) was
obtained in the same manner as that in Synthesis Example 3-1,
except that refining was carried out by column chromatography in
place of activated carbon filtration (produced amount: 37.9 g (164
mmol), yield: 82%, melting point: 115.degree. C.).
The refining method was as follows: 45 g of the crude product and
20 mL of a mixed solution of methylene chloride and acetonitrile
(4:1 (vol. ratio)) were added to a 500 mL beaker and stirred for 5
minutes for dissolution. Next, refining was carried out by column
chromatography using aluminum oxide (450 cc) as a fixed phase and a
mixed solvent of methylene chloride and acetonitrile (4:1 (vol.
ratio), 2.5 L) as a moving phase to obtain triethylmethylammonium
tetracyanoborate, an desired product. The product showed an NMR
spectrum and various physical properties same as those of the
product of Synthesis Example 3-1.
Synthesis Example 3-3
Tetrabutylammonium Tetracyanoborate (Bu.sub.4NTCB) Synthesis
Tetrabutylammonium tetracyanoborate (white solid) as a desired
product was obtained in the same manner as that in Synthesis
Example 3-1, except that 64.5 g (200 mmol) of tetrabutylammonium
bromide was employed in place of Et.sub.3MeNCl employed in
Synthesis Example 3-1 (produced amount: 60.0 g (196 mmol), yield:
98%, melting point: 90.degree. C.). The product showed an NMR
spectrum and various physical properties similar to those of the
product of Synthesis Example 1-1.
Ion conductivity (25.degree. C.): 0.009 S/cm
Thermal decomposition starting temperature: 210.degree. C.
Potential window: -3.2 V to 2.0 V
Synthesis Example 3-4
1-ethyl-3-Methylimidazolium Tetracyanoborate (EtMeImTCB)
Synthesis
As a desired product, 1-ethyl-3-methylimidazolium tetracyanoborate
(light yellow liquid) was obtained in the same manner as that in
Synthesis Example 3-1, except that 38.2 g (200 mmol) of
1-ethyl-3-methylimidazolium bromide was employed in place of
Et.sub.3MeNCl (produced amount: 24.9 g (110 mmol), yield: 55%,
melting point: 15.degree. C.). The product showed an NMR spectrum
and various physical properties similar to those of the product of
Synthesis Example 1-2.
Ion conductivity (25.degree. C.): 0.021 S/cm
Thermal decomposition starting temperature: 330.degree. C.
Potential window: -2.4 V to 2.0 V
Synthesis Example 3-5
Triethylammonium Tetracyanoborate (Et.sub.3NHTCB) Synthesis 1
Triethylammonium tetracyanoborate (light yellow liquid), as a
desired product, was obtained in the same manner as that in
Synthesis Example 3-1, except that 20.2 g (200 mmol) of
triethylamine was employed in place of Et.sub.3MeNCl (produced
amount: 23.8 g (110 mmol), yield: 60%, melting point: 150.degree.
C.). The product showed an NMR spectrum and various physical
properties similar to those of the product of Synthesis Example
1-3.
Ion conductivity (25.degree. C.): 0.018 S/cm
Thermal decomposition starting temperature: 285.degree. C.
Potential window: -1.7 V to 2.0 V
Synthesis Example 3-6
Triethylammonium Tetracyanoborate (Et.sub.3NHTCB) Synthesis 2
Triethylammonium tetracyanoborate (light yellow liquid), as a
product, was obtained in the same manner as that in Synthesis
Example 3-1, except that 27.5 g (200 mmol) of triethylammonium
chloride was employed in place of Et.sub.3MeNCl (produced amount:
23.8 g (110 mmol), yield: 60%, melting point: 150.degree. C.). The
product showed an NMR spectrum and various physical properties
similar to those of the product of Synthesis Example 3-5.
Synthesis Example 3-7
Tetraethylammonium Tetracyanoborate (Et.sub.4NTCB) Synthesis 1
Tetraethylammonium tetracyanoborate (white solid), as a product,
was obtained in the same manner as that in Synthesis Example 3-1,
except that 33.1 g (200 mmol) of tetraethylammonium chloride was
employed in place of Et.sub.3MeNCl (produced amount: 46.6 g (190
mmol), yield: 95%, melting point: 150.degree. C.). The product
showed an NMR spectrum and various physical properties similar to
those of the product of Synthesis Example 1-5.
Ion conductivity (25.degree. C.): 0.015 S/cm
Thermal decomposition starting temperature: 220.degree. C.
Potential window: -3.0 V to 2.0 V
Synthesis Example 3-8
Triethylmethylammonium Tetracyanoborate Synthesis 3
The same operation as that of Synthesis Example 3-1 was carried
out, except that a 1 L pressure-resistant container (made of
stainless steel, usable in pressurized condition at 5 kPa) was used
in place of the eggplant flask and TMSCl generated as a byproduct
during the reaction was not extracted to obtain light yellow solid
triethylmethylammonium tetracyanoborate (produced amount: 33.3 g
(144 mmol), yield: 72%, melting point: 115.degree. C.) as a
product. The obtained product showed an NMR spectrum and various
physical properties similar to those of the product of Synthesis
Example 3-1.
Synthesis Example 3-9
Tetrabutylammonium Tetracyanoborate (Bu.sub.4NTCB) Synthesis 2
Tetrabutylammonium tetracyanoborate (white solid), as a product,
was obtained in the same manner as that in Synthesis Example 3-3,
except that 20.8 g (200 mmol) of trimethyl borate was employed in
place of boron trichloride and the reaction container was heated to
170.degree. C. (produced amount: 50.0 g (140 mmol), yield: 70%,
melting point: 90.degree. C.). The product showed an NMR spectrum
and various physical properties similar to those of the product of
Synthesis Example 3-3.
Synthesis Example 3-10
Tetrabutylammonium Tetracyanoborate (Bu.sub.4NTCB) Synthesis 3
Tetrabutylammonium tetracyanoborate (white solid), as a product,
was obtained in the same manner as that in Synthesis Example 3-3,
except that 29.2 g (200 mmol) of triethyl borate was employed in
place of boron trichloride and the reaction container was heated to
170.degree. C. (produced amount: 50.0 g (140 mmol), yield: 70%,
melting point: 90.degree. C.). The product showed an NMR spectrum
and various physical properties similar to those of the product of
Synthesis Example 3-3.
Synthesis Example 3-11
Tetrabutylammonium Tetracyanoborate (Bu.sub.4NTCB) Synthesis 4
Tetrabutylammonium tetracyanoborate (white solid), as a product,
was obtained in the same manner as that in Synthesis Example 3-3,
except that 28.4 g (200 mmol) of boron trifluoride diethyl ether
complex was employed in place of boron trichloride and the reaction
container was heated to 170.degree. C. (produced amount: 53.6 g
(150 mmol), yield: 75%, melting point: 90.degree. C.). The product
showed an NMR spectrum and various physical properties similar to
those of the product of Synthesis Example 3-3.
Synthesis Example 3-12
Triethylmethylammonium Tetracyanoborate Synthesis 4
Triethylmethylammonium tetracyanoborate (light yellow solid), as a
product, was obtained in the same manner as that in Synthesis
Example 3-1, except that butyl acetate was employed in place of
p-xylene (produced amount: 27.7 g (120 mmol), yield: 55%, melting
point: 115.degree. C.). The product showed an NMR spectrum and
various physical properties similar to those of the product of
Synthesis Example 3-1.
Synthesis Example 3-13
Triethylmethylammonium Tetracyanoborate Synthesis 5
Reaction same as Synthesis Example 3-1 was carried out and 69.5 g
(640 mmol) of TMSCl discharged out through the reflux discharge
part was added to a flask (capacity 500 mL) equipped with a
stirring device and then 64.7 g (640 mmol) of triethylamine and
17.3 g (640 mmol) of hydrogen cyanide were added at room
temperature (25.degree. C.) and stirred overnight. The obtained
product was distilled to obtain TMSCN (colorless liquid, produced
amount: 57.1 g (576 mmol), yield: 90%).
Triethylmethylammonium tetracyanoborate was obtained in the same
manner as that in Synthesis Example 3-1, except that 52.1 g (525
mmol) of TMSCN obtained by using TMSCl, a reaction byproduct, as a
raw material and 12.3 g (105 mmol) of BCl.sub.3 and 15.9 g (105
mmol) of TEMACl were used (produced amount: 19.8 g (86 mmol),
yield: 82%, melting point: 115.degree. C.). The obtained product
showed an NMR spectrum and various physical properties similar to
those of the product of Synthesis Example 3-1.
Synthesis Example 3-14
Tetramethylammonium Tetracyanoborate Synthesis
Tetramethylammonium tetracyanoborate (white solid), as a product,
was obtained in the same manner as that in Synthesis Example 3-1,
except that 21.9 g (200 mmol) of tetramethylammonium chloride was
employed in place of Et.sub.3MeNCl (produced amount: 26.5 g (140
mmol), yield: 70%,). .sup.1H-NMR(d6-DMSO) .delta. 3.08(s, 12H)
.sup.13C-NMR(d6-DMSO) .delta. 121.9(m), 55.3(s)
.sup.11B--NMR(d6-DMSO) .delta. -39.6(s)
Synthesis Example 3-15
Ammonium Tetracyanoborate Synthesis
Ammonium tetracyanoborate (white solid), as a product, was obtained
in the same manner as that in Synthesis Example 3-1, except that
10.7 g (200 mmol) of ammonium chloride was employed in place of
Et.sub.3MeNCl (produced amount: 8.0 g (60 mmol), yield: 30%,).
.sup.1H-NMR(d6-DMSO) .delta. 6.about.7(broad,4H)
.sup.13C-NMR(d6-DMSO) .delta. 121.9(m) .sup.11B--NMR(d6-DMSO)
.delta. -39.6(s)
Synthesis Example 3-16
Tributylammonium Tetracyanoborate Synthesis
Tributylammonium tetracyanoborate (yellow solid), as a product, was
obtained in the same manner as that in Synthesis Example 3-1,
except that 44.4 g (200 mmol) of tributylammonium chloride was
employed in place of Et.sub.3MeNCl (produced amount: 48.2 g (160
mmol), yield: 80%). .sup.1H-NMR(d6-DMSO) .delta. 2.98(m,6H),
1.4.about.1.8(m,6H), 1.2.about.1.3(m,6H), 0.94(m,9H)
.sup.13C-NMR(d6-DMSO) .delta. 121.9(m), 52.7(s), 26.2(s), 20.3(s),
14.4(s) .sup.11B--NMR(d6-DMSO) .delta. -39.6(s)
Synthesis Example 3-17
Lithium Tetracyanoborate Synthesis
A beaker having a capacity of 500 mL and equipped with a stirring
device was loaded with 48.2 g (160 mmol) of tributylammonium
tetracyanoborate obtained by Synthesis Example 3-16, 200 g of butyl
acetate, 4.6 g (192 mmol) of lithium hydroxide monohydrate, and 200
g of ultrapure water and the contents were stirred for 1 hour.
Thereafter, the mixed solution was transferred to a separatory
funnel and kept still and the mixed solution was separated into two
layers. Between the layers, the lower layer (water layer) was
separated and concentrated to give a light yellow solid, the
obtained light yellow solid was mixed with 200 g of acetonitrile
and stirred. Successively, the obtained solution was filtered with
a membrane filter (0.2 .mu.m, made of PTFE) and solvent was
evaporated to obtain lithium tetracyanoborate (white solid), a
desired product (produced amount: 13.6 g (112 mmol), yield: 70%).
.sup.7Li-NMR(d6-DMSO).delta. 0.02(s) .sup.13C-NMR(d6-DMSO).delta.
121.9(m) .sup.11B--NMR(d6-DMSO).delta. -39.6(s)
Synthesis Example 3-18
Triethylmethylammonium Tetracyanoborate Synthesis 6
The same reaction as that in Synthesis Example 3-1 was carried out,
and 69.5 g (640 mmol) of TMSCl extracted through the reflux
discharge part was added to a flask (capacity 500 mL) equipped with
a stirring device and next, 103.2 g (640 mmol) of
hexamethyldisilazane and 51.9 g (1919 mmol) of hydrogen cyanide
were added and the mixture was stirred overnight. The obtained
product was distilled to obtain TMSCN (colorless liquid, produced
amount: 171.4 g (1727 mmol), yield: 90%).
Triethylmethylammonium tetracyanoborate was obtained in the same
manner as that in Synthesis Example 3-1, except that 52.1 g (525
mmol) of TMSCN obtained by using TMSCl, a reaction byproduct, as a
raw material and 12.3 g (105 mmol) of boron trichloride, and 15.9 g
(105 mmol) of Et.sub.3MeNCl were used (light yellow solid, produced
amount: 19.8 g (86 mmol), yield: 82%, melting point: 115.degree.
C.). The obtained product showed an NMR spectrum and various
physical properties similar to those of the product of Synthesis
Example 3-1.
Synthesis Example 3-19
Trimethylsilylammonium Tetracyanoborate (Me.sub.3SiTCB) Synthesis
1
Trimethylsilylammonium tetracyanoborate, as a product, was obtained
in the same manner as that in Synthesis Example 3-1, except that no
Et.sub.3MeNCl was employed. Produced amount was 1.9 g (10 mmol),
and yield was 90%.
Synthesis Example 3-20
Triethylmethylammonium Tetracyanoborate Synthesis 7
The same operation as that of Synthesis Example 3-1 was carried
out, except that 71.6 g (1100 mmol) of potassium cyanide was used
in place of trimethylsilyl cyanide, however triethylmethylammonium
tetracyanoborate, an desired product, was not at all obtained.
In the third production method of the invention, since the activity
deterioration of reaction by a reaction byproduct is hardly caused,
an ionic compound containing tetracyanoborate ion can be produced
at a higher yield as compared that by a conventional method.
Further, in the case an ammonium salt is used, an ionic compound
containing an organic cation can be produced in one step.
Synthesis Example 3-21
Tributylammonium Tetracyanoborate Synthesis 2
The same operation as that of Synthesis Example 3-16 was carried
out except that 42.5 g (200 mmol) of tributylammonium cyanide in
place of tetrabutylammonium chloride, and 84.8 g (855 mmol) of
trimethylsilyl cyanide were used to obtain yellow solid
tributylammonium tetracyanoborate as a product (produced amount:
42.5 g (141 mmol), yield: 75%). The obtained product showed an NMR
spectrum and various physical properties similar to those of the
product of Synthesis Example 3-16.
Example 4
In Example 4, an ionic compound having tetracyanoborate as an anion
was synthesized by using hydrogen cyanide (HCN) as a starting
material.
Synthesis Example 4-1
Tributylammonium Tetracyanoborate Synthesis
A 200 ml three-neck flask equipped with a heating device, a
stirring device and a reflux condenser was purged with nitrogen and
10.2 g (55 mmol) of tributylamine and 1.49 g (55 mmol) of hydrogen
cyanide were added at room temperature and stirred for 1 hour.
Successively, 1.17 g (10 mmol) of boron trichloride and 100 ml of
p-xylene were further added and the contents were heated and
refluxed for 2 days at 150.degree. C. After 30 g of butyl acetate
was added to the obtained black solution and stirred at room
temperature, 9 g of activated carbon (Carborafin (registered trade
name)-6 manufactured by Japan EnviroChemicals, Ltd.) was added
thereto and stirred for 20 minutes at room temperature. The
obtained activated carbon suspension was filtered with a membrane
filter (0.5 .mu.m, made of PTFE) and operation involving washing
activated carbon on the filter with 30 g of butyl acetate was
repeated 5 times. Obtained filtrate and washing solution were mixed
and dried by removing the solvent to obtain black solid.
Next, the obtained black solid was mixed with 8 g of hydrogen
peroxide water and stirred for 1 hour at 50.degree. C., thereafter,
40 g of butyl acetate was added to the obtained solution and
stirred further for 20 minutes at room temperature and the solution
was kept still for 10 minutes and successively, the butyl acetate
layer was separated, removed the solvent therefrom and dried to
obtain an oily brown tributylammonium tetracyanoborate
(Bu.sub.3NHTCB) (produced amount 1.21 g (4 mmol), yield 40%).
.sup.1H-NMR(d6-DMSO).delta. 8.8 (br, 1H), 2.99 (dd,J=8.0 Hz,J=16.4
Hz,6H), 1.52 (m,6H), 1.28 (m,6H), 0.88 (m,9H)
.sup.13C-NMR(d6-DMSO).delta. 121.9 (m), 46.0 (s), 8.8 (s)
.sup.11B--NMR(d6-DMSO).delta. -39.6 (s)
Synthesis Example 4-2
Triethylammonium Tetracyanoborate Synthesis
Triethylammonium tetracyanoborate was obtained in the same manner
as that in Synthesis Example 4-1, except that 5.58 g (55 mmol) of
triethylamine was employed in place of tributylamine (brown solid,
produced amount: 0.65 g (3 mmol), yield: 30%). The NMR data of the
obtained triethylammonium tetracyanoborate is indicated below. The
various physical properties measured by the above-mentioned
measurement methods are as follows.
Ion conductivity (25.degree. C.): 0.018 S/cm
Thermal decomposition starting temperature: 285.degree. C.
Potential window: -1.7 V to 2.0 V .sup.1H-NMR(d6-DMSO) .delta. 8.83
(s,1H), 3.10 (q,J=7.2 Hz,6H), 1.17 (t,J=7.2 Hz,9H)
.sup.13C-NMR(d6-DMSO) .delta. 121.9 (m), 46.0 (s), 8.8 (s)
.sup.11B--NMR(d6-DMSO) .delta. -39.6 (s)
According to the invention, an ionic compound containing
tetracyanoborate can be obtained by using economical hydrogen
cyanide as a starting material.
According to the fourth production method of the invention, since
hydrogen cyanide is used as a cyanide source, an ionic compound
containing tetracyanoborate can be obtained economically as
compared with a conventional method.
Example 5
In Example 5, the amount of impurities contained in each ionic
compound obtained by the following Synthesis Examples 5 to 11 was
measured. Measurement methods of the respective type impurities are
as follows.
[Measurement of Metal Component Content]
(1) Measurement by ICP (Measurement of Na and Si)
Each 2 g of respective ionic compounds obtained by the following
Synthesis Examples 5 to 11 were diluted with ultrapure water
(higher than 18.2 .OMEGA.cm) 10 to 100 times as much to obtain
measurement solutions, and amounts of Na and Si contained in each
ionic compound were measured by using an ICP emission
spectrophotometer ICPE-9000 (manufactured by Shimadzu
Corporation).
(2) Measurement by Ion Chromatography (Measurement of Halide
Ions)
Each 0.3 g of respective ionic compounds obtained by the following
Synthesis Examples were diluted with ultrapure water (higher than
18.2 .OMEGA.cm) 100 to 1000 times as much to obtain measurement
solutions, and the amount of halide ions contained in each ionic
compound was measured by using ion chromatography system ICS-3000
(manufactured by Nippon Dionex K.K.).
Separation mode: ion exchange
Detector: Electric conductivity detector CD-20
Column: Anion analysis column AS 17-C (manufactured by Nippon
Dionex K.K.).
(3) Measurement by Ion Chromatography (Measurement of CN.sup.-)
Each 0.1 g of respective ionic compounds obtained by the following
Synthesis Examples were diluted with ultrapure water (higher than
18.2 .OMEGA.cm) 10000 times as much to obtain measurement
solutions, and the amount of cyanide ion (CN.sup.-) contained in
each ionic compound was measured by using ion chromatography system
ICS-1500 (manufactured by Japan Dionex Co., Ltd.).
Separation mode: ion exchange
Eluent: 10 mmol aqueous H.sub.2SO.sub.4 solution
Regeneration solution: 0.5 mmol aqueous NaOH solution
Detector: Electrochemical detector ED-50A
Column: Anion analysis column ICE-AS1
[Water Measurement]
The amount of water in each sample was measured by using water
measurement apparatus "AQ-2000" manufactured by Hiranuma Sangyo
Co., Ltd. The sample injection amount was 0.1 ml and "Hydranal
Aqualite RS-A" (commercialized by Hiranuma Sangyo Co., Ltd.) was
used as an anolyte and "Aqualite CN" was used as a catholyte
(manufactured by Kanto Chemical Co., Inc.). Each sample was
injected through a sample injection inlet by using an injection
syringe for avoiding contact with atmospheric air.
Hereinafter, in Synthesis Example 5, ionic compound synthesis was
carried out by using starting materials containing trimethylsilyl
cyanide.
Synthesis Example 5
Synthesis Example 5-1
Triethylmethylammonium Tetracyanoborate Synthesis
<Synthesis of Crude Production>
A 1 L eggplant flask equipped with a stirring device, a reflux
condenser, a discharge device, and dripping funnel was loaded with
30.3 g (200 mmol) of previously heated and dried
triethylmethylammonium chloride (Et.sub.3MeNCl). After the
container was purged with nitrogen, 109.0 g (1100 mm) of
trimethylsilyl cyanide (TMSCN) was added at room temperature and
stirred and mixed. Next, 200 mL (200 mmol) of a p-xylene solution
of 1 mol/L boron trichloride (BCl.sub.3) was gradually and dropwise
added through the dripping funnel. On completion of the dropwise
addition, the reaction container was heated to 150.degree. C. and
reaction was carried out while trimethylsilyl chloride (TMSCl,
boiling point: about 57.degree. C.) generated as a byproduct being
discharged through a reflux discharge part.
After 30 hour heating and stirring, the inside pressure of the
reaction container was reduced by a diaphragm pump and a p-xylene
solution of TMSCN was removed through the reflux discharge part. In
the container, crude triethylmethylammonium tetracyanoborate
(Et.sub.3MeNTCB) was produced.
<Activated Carbon Treatment>
Next, 46.0 g of the obtained crude product was dissolved in ethyl
acetate in a 500 mL beaker equipped with a stirring device to
obtain a 10 wt % ethyl acetate solution, and 65 g of activated
carbon (Carborafin (registered trade name) manufactured by Japan
EnviroChemicals, Ltd.) was added thereto and heated by a water bath
until the inner temperature became 50.degree. C. Successively,
after being stirred for 10 minutes at 50.degree. C., the obtained
activated carbon suspension was filtered with a membrane filter
(0.2 .mu.m, made of PTFE). With respect to activated carbon on the
filter, operation involving suspending the activated carbon in
ethyl acetate of a weight 3 times as much as that of the crude
product and washing the crude product by stirring the suspension
for 10 minutes at 50.degree. C. was repeated 5 times. Obtained
filtrate and washing solution were mixed and after the ethyl
acetate was removed in reduced pressure, the obtained product was
heat-dried at 50.degree. C. in vacuum to obtain a light yellow
solid of Et.sub.3MeNTCB (produced amount: 37 g (160 mmol), yield:
80%, melting point: 115.degree. C.).
<Oxidizing Agent Treatment>
The obtained Et.sub.3MeNTCB and hydrogen peroxide (aqueous 30 wt %
H.sub.2O.sub.2 solution) in a weight 2.25 time as much as that of
Et.sub.3MeNTCB were added to a beaker equipped with a stirring
device and a reflux condenser, and stirred for 60 minutes at
50.degree. C.
<Extraction Treatment>
Next, butyl acetate in a weight 9 times as much as that of
Et.sub.3MeNTCB, which had been subjected to the activated carbon
treatment, was added to the H.sub.2O.sub.2 solution of
Et.sub.3MeNTCB and the mixed solution was stirred. Thereafter, the
mixed solution was transferred to a container (capacity: 1000 mL)
for centrifugal separation and then the container was shaken for 90
seconds and subjected to centrifugal separation (1700 rpm, 10
minutes). The obtained butyl acetate layer (supernatant, an organic
layer) was concentrated.
<Dry>
The butyl acetate layer containing Et.sub.3MeNTCB which was
obtained by the extraction treatment was further heated for 30
minutes (80.degree. C.) in reduced pressure and the coarsely dried
Et.sub.3MeNTCB was pulverized with a mortar to obtain a powder. The
obtained powder was spread on a tray on which a Teflon (registered
trade name) sheet was spread and set in a vacuum drier and dried
for 3 days at 80.degree. C. in reduced pressure.
The NMR analysis results of the obtained Et.sub.3MeNTCB are shown
below. The ion component amounts in Et.sub.3MeNTCB measured by the
above-mentioned method are shown in Table 1. The product showed an
NMR spectrum same as that of Synthesis Example 1-4.
Synthesis Example 5-2
The same operation as that of Synthesis Example 5-1 was carried out
except that, in the oxidizing agent treatment, 83 mL of an aqueous.
30 weight % sodium perchlorate solution was used in place of
hydrogen peroxide solution to synthesize Et.sub.3MeNTCB.
Synthesis Example 5-3
Et.sub.3MeNTCB was synthesized in the same manner as that in
Synthesis Example 5-1, except that no activated carbon treatment
was carried out after the synthesis of cude product.
Synthesis Example 5-4
Et.sub.3MeNTCB synthesized in Synthesis Example 5-1 after the
activated carbon treatment was used as a measurement sample.
Synthesis Example 5-5
Et.sub.3MeNTCB in amount of 46 g produced in Synthesis Example 5-1
before the activated carbon treatment was mixed with 104 ml of
aqueous 0.01 mol/L NaOH solution and stirred for 60 minutes at
50.degree. C. Next, butyl acetate in a weight 9 times as much as
that of Et.sub.3MeNTCB was added to the NaOH solution of
Et.sub.3MeNTCB and extraction treatment was carried out in the same
manner as in Synthesis Example 5-1 to synthesize Et.sub.3MeNTCB
(without activated carbon treatment and oxidizing agent
treatment).
Synthesis Example 6
Synthesis Example 6-1
Tetrabutylammonium tetracyanoborate synthesis
As a product, a white solid tetrabutylammonium tetracyanoborate
(Bu.sub.4NTCB) was obtained by synthesis of a crude product and
activated carbon treatment in the same manner as in Synthesis
Example 5-1, except that 64.5 g (200 mmol) of tetrabutylammonium
bromide was used in place of Et.sub.3MeNCl used in Synthesis
Example 5 (produced amount; 60.0 g (164 mmol), yield: 82%, melting
point: 90.degree. C.). The product showed an NMR spectrum same as
that of Synthesis Example 1-1.
Synthesis Example 6-2
Bu.sub.4NTCB obtained in Synthesis Example 6-1 was mixed with
hydrogen peroxide solution (aqueous 30 wt % H.sub.2O.sub.2
solution) in a weight 2.25 times as much as that of Bu.sub.4NTCB
and stirred for 60 minutes at 50.degree. C. Thereafter, extraction
and drying treatment were carried out in the same manner as in
Synthesis Example 5-1 to obtain a white solid of Bu.sub.4NTCB.
(produced amount; 45 g (120 mmol), yield: 62%).
Synthesis Example 7
Synthesis Example 7-1
1-Ethyl-3-Methylimidazolium Tetracyanoborate Synthesis
Synthesis of a crude product and activated carbon treatment were
carried out in the same manner as in Synthesis Example 5-1, except
that 38.2 g (200 mmol) of 1-ethyl-3-methylimidazolium bromide was
used in place of Et.sub.3MeNCl to obtain a light yellow oil of
1-ethyl-3-methylimidazolium tetracyanoborate (EtMeImTCB) as a
product (produced amount; 24.9 g (110 mmol), yield: 55%, melting
point: 15.degree. C.). The product showed an NMR spectrum same as
that of Synthesis Example 1-2.
Synthesis Example 7-2
EtMeImTCB obtained in Synthesis Example 7-1 was mixed with hydrogen
peroxide solution (aqueous 30 wt % H.sub.2O.sub.2 solution) in a
weight 2.25 times as much as that of EtMeImTCB and stirred for 60
minutes at 50.degree. C. Thereafter, extraction and drying
treatment were carried out in the same manner as in Experiment
Example 1-1 to obtain a light yellow oil of EtMeImTCB (produced
amount; 18 g (80 mmol), yield: 40%).
Synthesis Example 8
Synthesis Example 8-1
Triethylammonium Tetracyanoborate Synthesis
Synthesis of a crude product and activated carbon treatment were
carried out in the same manner as in Synthesis Example 5-1, except
that 20.2 g (200 mmol) of triethylamine was used in place of
Et.sub.3MeNCl to obtain a light yellow solid of triethylammonium
tetracyanoborate (Et.sub.3NHTCB) as a product (produced amount;
23.8 g (110 mmol), yield: 60%, melting point: 150.degree. C. The
product showed an NMR spectrum same as that of Synthesis Example
1-3.
Synthesis Example 8-2
Et.sub.3NHTCB obtained in Synthesis Example 8-1 was mixed with
hydrogen peroxide solution (aqueous 30 wt % H.sub.2O.sub.2
solution) in a weight 2.25 times as much as that of Et.sub.3NHTCB
and stirred for 60 minutes at 50.degree. C. Thereafter, extraction
and drying treatment were carried out in the same manner as in
Synthesis Example 5-1 to obtain a light yellow solid of
Et.sub.3NHTCB (produced amount; 17 g (80 mmol), yield: 40%).
Synthesis Example 9
Synthesis Example 9-1
Tetraethylammonium Tetracyanoborate Synthesis
Synthesis of a crude product and activated carbon treatment were
carried out in the same manner as in Synthesis Example 5-1, except
that 33.1 g (200 mmol) of tetraethylammonium chloride was used in
place of Et.sub.3MeNCl to obtain a white solid of
tetraethylammonium tetracyanoborate (Et.sub.4NTCB) as a product
(produced amount; 46.6 g (190 mmol), yield: 95%, melting point:
150.degree. C.). The product showed an NMR spectrum same as that of
Synthesis Example 1-5.
Synthesis Example 9-2
Et.sub.4NTCB obtained in Synthesis Example 9-1 was mixed with
hydrogen peroxide solution (aqueous 30 wt % H.sub.2O.sub.2
solution) in a weight 2.25 times as much as that of Et.sub.4NTCB
and stirred for 60 minutes at 50.degree. C. Thereafter, extraction
and drying treatment were carried out in the same manner as in
Synthesis Example 5-1 to obtain a light yellow solid of
Et.sub.4NTCB (produced amount; 35 g (144 mmol), yield: 72%).
Synthesis Example 10
Synthesis Example 10-1
Tetramethylammonium Tetracyanoborate Synthesis
Synthesis of a crude product and activated carbon treatment were
carried out in the same manner as in Synthesis Example 5-1, except
that 21.9 g (200 mmol) of tetramethylammonium chloride was used in
place of Et.sub.3MeNCl to obtain a white solid of
tetramethylammonium tetracyanoborate (Me.sub.4NTCB) as a product
(produced amount; 26.5 g (140 mmol), yield: 70%).
.sup.1H-NMR(d6-DMSO) .delta. 3.08(s, 12H) .sup.13C-NMR(d6-DMSO)
.delta. 121.9(m),55.3(s) .sup.11B--NMR(d6-DMSO) .delta.
-39.6(s)
Synthesis Example 10-2
Me.sub.4NTCB obtained in Synthesis Example 10-1 was mixed with
hydrogen peroxide solution (aqueous 30 wt % H.sub.2O.sub.2
solution) in a weight 2.25 times as much as that of Me.sub.4NTCB
and stirred for 60 minutes at 50.degree. C. Thereafter, extraction
and drying treatment were carried out in the same manner as in
Synthesis Example 5-1 to obtain a light yellow solid of
Me.sub.4NTCB (produced amount; 11 g (100 mmol), yield: 50%).
Synthesis Example 11
Synthesis Example 11-1
Tributylmethylammonium Tetracyanoborate Synthesis
Synthesis of a crude product and activated carbon treatment were
carried out in the same manner as in Synthesis Example 5-1 except
that 44.4 g (200 mmol) of tributylammonium chloride was used in
place of Et.sub.3MeNCl to obtain a yellow solid of tributylammonium
tetracyanoborate (Bu.sub.3NHTCB) as a product (produced amount;
48.2 g (160 mmol), yield: 80%). The product showed an NMR spectrum
same as that of Synthesis Example 3-16.
Synthesis Example 11-2
Bu.sub.3NHTCB obtained in Synthesis Example 11-1 was mixed with
hydrogen peroxide solution (aqueous 30 wt % H.sub.2O.sub.2
solution) in a weight 2.25 times as much as that of Bu.sub.3NHTCB
and stirred for 60 minutes at 50.degree. C. Thereafter, extraction
and drying treatment were carried out in the same manner as in
Synthesis Example 5-1 to obtain a yellow solid of Bu.sub.3NHTCB
(produced amount; 39 g (0.13 mmol), yield: 65%).
The various kinds of ion components contained in each ionic
compound produced in Synthesis Examples 5 to 11 were measured by
the above-mentioned methods. The results are shown in Table 3. In
Table 3, "N.D." showed that the amount of an impure ion component
contained in a measurement sample was measurement limit (1 ppm) or
lower.
TABLE-US-00003 TABLE 3 Treatment Activated Oxidizing carbon agent
Extraction Cl/ppm Br/ppm CN/ppm Na/ppm Si/ppm Water/ppm Synthesis
employed H.sub.2O.sub.2 employed 4 -- 288 N.D. N.D. 83 Example 5-1
Synthesis employed NaClO.sub.4 employed 94 -- 10 1180 131 110
Example 5-2 Synthesis not H.sub.2O.sub.2 employed <1 -- 119 40
31 114 Example employed 5-3 Synthesis employed not not 350 -- 6700
32 22000 1750 Example employed employed 5-4 Synthesis employed
H.sub.2O.sub.2 NaOH 86 -- 550 744 2724 530 Example extraction 5-5
Synthesis employed not not 570 -- 1600 32 16900 1840 Example
employed employed 6-1 Synthesis employed H.sub.2O.sub.2 employed 3
-- 161 9 236 80 Example 6-2 Synthesis employed not not 630 480 2990
5 50300 1620 Example employed employed 7-1 Synthesis employed
H.sub.2O.sub.2 employed 5 <1 86 10 6 83 Example 7-2 Synthesis
employed not not 439 -- 152 192 28200 3200 Example employed
employed 8-1 Synthesis employed H.sub.2O.sub.2 employed <1 --
110 N.D. 12 66 Example 8-2 Synthesis employed not not 1210 -- 6740
9 3000 4800 Example employed employed 9-1 Synthesis employed
H.sub.2O.sub.2 employed <1 -- 119 39 31 114 Example 9-2
Synthesis employed not not 2300 -- 4320 8 42100 2200 Example
employed employed 10-1 Synthesis employed H.sub.2O.sub.2 employed 4
-- 288 N.D. N.D. N.D. Example 10-2 Synthesis employed not not 3200
-- 3420 21 19800 2400 Example employed employed 11-1 Synthesis
employed H.sub.2O.sub.2 employed 5 -- 268 8 18 100 Example 11-2
From the results of Synthesis Examples 5 to 11, it can be
understood that Si, cyanide ion (CN.sup.-), and halide ion
(Cl.sup.- or Br.sup.-) remaining in the ionic compound are
decreased by the oxidizing agent treatment by bringing the ionic
compound into contact with an oxidizing agent.
Further, from the results of Synthesis Example 5, it can be
understood that the effect of the oxidizing agent treatment became
furthermore efficient by combination with activated carbon
treatment and extraction treatment (comparison of Synthesis Example
5-1 and Synthesis Example 5-3) and furthermore, it can also be
understood that the water content in the ionic compound are further
decreased in the case hydrogen peroxide is used as an oxidizing
agent by comparing Synthesis Example 5-1 and Synthesis Example
5-2.
That is, according to the invention, a high purity ionic compound
with decreased content of impure ions which are contained in the
starting materials and are inevitably mixed during production is
obtained.
Example 6
In Example 6, the highest occupied molecular orbital energy level
of various kind of anions having a structure defined by the general
formula [(NC).sub..nu.--X.sup.d-] was calculated (Experiment
Example 5) and the withstand voltage range LSV of actually
synthesized anions was measured (Experiment Example 6).
Experiment Example 5
Calculation of Highest Occupied Molecular Orbital Energy Level
Calculation of the highest occupied molecular orbital energy level
of various kinds of anions shown in Table 4 below was carried out,
employing GAUSSIAN 03 (manufactured by GAUSSIAN, Inc.) and using
B3LYP/6-311+G(2d, p) for the basis function. The calculation
results of the highest occupied molecular orbital energy level are
shown in Table 4.
TABLE-US-00004 TABLE 4 Energy level No Anion [eV] 1 OCN -0.856 2
SCN -1.082 3 N(CN).sub.2 -1.776 4 C(CN).sub.2 -1.983 5 Se(CN).sub.3
-3.745 6 B(CN).sub.4 -5.809 7 Al(CN).sub.4 -6.107 8 Ga(CN).sub.4
-6.077 9 Si(CN).sub.5 -5.961 10 Ge(CN).sub.5 -5.735 11 P(CN).sub.6
-6.561 12 As(CN).sub.6 -6.744 13 B(CN).sub.3F -5.421 14
B(CN).sub.2F.sub.2 -4.974 15 B(CN)F.sub.3 -4.642 16 BF.sub.4 -4.499
17 PF.sub.6 -5.319 18 AsF.sub.6 -5.862
Experiment Example 6
Linear Sweep Voltammetry (LSV Measurement)
In Experiment Example 6, withstand voltage range LSV of actually
synthesized anions was measured. LSV measurement was carried out as
follows.
[Measurement of Withstand Voltage Range LSV]
The withstand voltage range was measured by carrying out LSV
measurement by a standard voltammetry tool HSV-100 (trade name,
manufactured by Hokuto Denko Corporation) using a tripolar cell in
a glove box at 30.degree. C. atmosphere. The measurement conditions
are as follows.
(Measurement Condition)
Working electrode: Glassy carbon electrode, Reference electrode; Ag
electrode, counter electrode: Platinum electrode
Solution concentration: 1 mol/L
Solvent: propylene carbonate
Sweeping speed: 100 mV/s
Sweeping range: spontaneous potential to .+-.5V
Experiment Example 6-1
Et.sub.3MeNTCB obtained in Synthesis Example 1-3 was dissolved in
dehydrated propylene carbonate (manufactured by Kishida Chemical
Co., Ltd.) to have a concentration of 1 mol/L and subjected to LSV
measurement. The result is shown in FIG. 1.
Experiment Example 6-2
A 2.0 mol/LPC solution of commercialized triethylmethylammonium
tetrafluoroborate (TEMABF.sub.4) (manufactured by Kishida Chemical
Co., Ltd.) was diluted to 1.0 mol/L and then subjected to LSV
measurement. The result is shown in FIG. 2.
In Table 4, the anions shown in No. 6 to 11 had the highest
occupied molecular orbital energy level lower than -5.5 eV and it
is implied that the anions had wide potential window. Actually, as
shown in Experiment Example 6-1 (FIG. 1), although slight electric
current was observed around 2 V, electric current in Et.sub.3MeNTCB
having the HOMO level of -5.809 eV was scarcely observed in a
voltage range higher than that and thus it can be understood that
Et.sub.3MeNTCB is a compound having a wider withstand voltage range
than Et.sub.3MeNBF.sub.4 shown in Experiment Example 6-2 (FIG.
2).
Since an ion-conductive material of the invention has a wide
potential window and contains no harmful substance such as F and
As, it can be used preferably for uses such as lithium ion
batteries, lithium ion capacitors, electric double layer
capacitors, and electrolytic capacitors.
Industrial Applicability
An ionic compound containing tetracyanoborate obtained by the
production method of the invention is used preferably for various
uses as constituent materials of various kinds of electrochemical
devices such as ion conductors (electrolytic solution materials or
the like), e.g., lithium secondary batteries, electrolytic
capacitors, electric double layer capacitors, lithium ion
capacitors, etc., a reaction solvent for organic synthesis, a
conductivity supply agent for polymers, a lubricant, a gas
absorbent, etc.
Especially, if an ionic compound of the invention is used, a highly
reliably electrolyte solution material and an additive such as a
conductivity supply agent and a lubricant is provided.
* * * * *